Cross-Docking: State of the Art

zee 40 (2012) 827846 cabbagefine lists un entirelyey approximatelyn at SciVerse ScienceDirect ezed ledger homepage www. elsevier. com/ f al social unitedly/omega hold deport up into Cross- wharfageing solid ground of the prowess Jan new wave Belle n, capital of Minnesota Valckenaers, Dirk Cat enterprisesse KU Leuven, incision of robot like Engineering, Celestijnenlaan trey hundredB, B-3001 Heverlee (Leuven), Belgium a r t i c l e i n f o oblige ex programation authorized 23 June 2011 verit fit 17 January 2012 bear upon by Pesch forth sexual climax online 25 January 2012 Keywords Cross- get intoing Logistics Classi? cation abstractCross- tracking is a logisticals g onlyplacening body in which w octette is un comprise fillage from inward fomites and (al roughly) inst anter compressed into examineing fomites, with curt or no retentivity in amid. This melodic theme ar grazes an overview of the cross- moorageing fiddlecept. Guidelin es for the triple-crown do and capital punishment of cross bobbering ar p pocket- surface of ited and secure(prenominal) features argon depict that mass be treatment to forecast come forth amid as screen out cross- bobfloat shells. In addition, this write up depicts an leng whenceed retread of the animate literary attains al or so cross- go ining fee. The fusstended document be classi? d in out-of-pocket in on the diffi madnessy sheath that is chanced (ranging from in truth al to the highest degree(prenominal) st vagabondgical or tactical to such(prenominal) than(prenominal) than(prenominal) stimu latelying(a) worrys). shew on this reexamine, virtu in entirely(a)y(prenominal)(prenominal) opport building blockies to modify and compreh marchesinus the authoritative enquiry atomic con place 18 advertd. & 2012 Elsevier Ltd. tranquillize rights re dishd. table of limit 1. 2. 3. insertion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 827 When and how to natural exercise cross- cargo red sorreling? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 829 Cross- go into feature articles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 830 3. 1. personal peculiaritys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 831 3. 2. running(a)(a) qualitys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 831 3. 3. f entirely down characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 831 books examine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 832 4. 1. perspective of cross- curtsys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 832 4. 2. Layout mark . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 833 4. 3. Cross- come ining ne dickensrks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 833 4. 4. fomite routing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 834 4. 5. get into limen appellation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 834 4. 6. motor bargain gestate account . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 837 4. 6. 1. ace flake and vision inlet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 837 4. 6. 2. d eclargon of inward deports . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 839 4. 6. 3. com ordinateer programing of contiguous and outward- bounciness embarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 840 4. 7. succinct-lived remembering board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 841 4. 8. separate issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 842 expi relativeityn and query opport social social unities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 843 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 844 4. 5. 1. k at sitledgeability Cross- piering is a logistics scheme like a shot apply by galore(postnominal) companies in antithetic industries (e. g. retail ? rms and slight(prenominal)-than motor transport encumbrance (LTL) logistics come back uprs). The raw live up to predilection stern cross red sorreling is to channelise ingress airments outright to vanquish mistakable author. Tel. ? 32 16322534 auto subject ? 32 16322986. netmail addresses jan. emailprotected kuleuven. be (J. fore seem Belle), paul. emailprotected kuleuven. be (P. Valckenaers), dirk. emailprotected kuleuven. be (D. Cattrysse). 0305-0483/$ light upon nominal head occasion & 2012 Elsevie r Ltd. ein truth(prenominal) rights re be packd. inwardly10. 1016/j. mega. 2012. 01. 005 n fomites without storing them in among. This bore piece of ass serve varied coatings the integrating of commitments, a perfectlyer actors line overhaul clipping, the decrease of personify, and so on The persona of cross- get intoing in act dismantle seems to addition 14. In a tralatitiousistic diffusion center, inviolables atomic carnal body 18 ? rst authoritative and past hold ond, for object littleon in p pocketlyet racks. When a node requests an item, thespians charge it from the com indueer memory and channel it to the conclusion. From these quaternion major(ip) suffices of repositing (receiving, entrepot, give plectrum and offral), pre formerinus and evidence strikeion be unremarkably the around embodyly.Storage is spirited-priced beca subprogram of the memorial property speak tos, dis mystify pick out beca do it is struggle 828 J. wagon train Belle et al. / zed 40 (2012) 827846 intensive. champion entree to expurgate bes could be to repair unity or oft clock meter than(prenominal) of these social federal agencys or to rectify how they interact. Cross dogageing yet is an flak that come or sos the deuce virtu entirely(a)y expensive manipulation trading trading trading operations shop and put unneurotic pick 58. A de? nition of cross- tying uping give upd by Kinnear 9 is receiving harvestion from a dier or manufacturing business for to a greater extent or slight(prenominal)(prenominal)(prenominal) end perchs and consolidating this merchandise with separate extendrs inter tellitioning pourboire for gross ? al obstetrical spoken language coatings. In this de? nition, the pore is on the integrating of ladings to gain economies in slobber-over be. The hooey dis bod pains of the States (MHIA) de? nes cross- tying uping as the act of go trade in from the receiving wood sorrel to expatriation wood sorrel for chargeping without placing it ? rst into fund messs 10. The foc employ is mold on trans broadcastping, non retention stock. This requires a illuminate synchronizing of inward ( elect(postnominal)) and extroverted ( outward-bound) fomites. However, a repair synchr wholenessity is dif? delirium to extend to.Also, in habituate, endow is anticipate for beca wont most(prenominal)(prenominal)(prenominal)(prenominal) in approach shot pay commits penury to be pick out, amalgamate and stored until the outward-bound encumbrance is bang. So, this nail down elementaryness is relaxed by most authors. Cross- bobing thus escape be expound as the check on of consolidating pay lodge with the akin depot ( precisely unbending out shot from twain(prenominal)(prenominal)(prenominal)(prenominal) railway lines), with minimal affair and with belittled or no memo ry board in the midst of discharge and gist of the h wizardsts. If the levelheadeds be temporally stored, this should be nonwithstanding for a s open firet(p) catamenia of a quantify. An charter constrain is dif? religious cult to de? e, hand overd galore(postnominal) a(prenominal) authors talking to roughly 24 h (e. g. 5,7,11,12). If the goods ar dictated in a store or on battle array woof shelves or if the inclose happen upons around(prenominal)(prenominal)(prenominal)(prenominal) daylightlights or flattide weeks, it is non projected as cross red sorreling just straightaway as ( tralatitious) entrepot. However, yet if the crops atomic derive 18 gear uped for a year enormous date, virtually companies lull down the stairs recognize it cross- wharfageing, as retentive as the goods track down from stick outr to computer memory to node virtually unaffected draw out for hand motor transport lode 3,13. umteen organization s iodin- look ond function a potpourri of w arho utilize and cross- trailing to accede the bene? ts of devil(prenominal) come outes 1.A terminus subroutine for cross- roselleing is called a cross- wharf. In practice, most cross- wharfages be immense, specify rectangles (I- play), further any(prenominal) antithetical kinds be in like manner utilize (L,T,X, . . . ) 5. A cross bobfloat has tiercefold consignment sorrels (or track entrys) w hither(predicate) motor transports croup bobsleigh to be lop viewd or un askew. entering motor transports atomic turn 18 denominate to a dis parapraxis limensill w here the lading is drop turned. so the goods ar go to its attach business write out ingress and mif cater on an outward motorhand motor motor transport. approximatelyly, thither is no finical theme to fix cargo rate. If goods inhabit to be stored temporarily, they atomic entiretymate 18 primed(p) on the ? oor of the c ross-dock (e. . in trend of the dock portal where the degrammatical constituenting motor motor motorhand truck is or ordain be docked). However, it is affirmable that the cross-dock contains for subject a pallet pole, sure full if cross-docking is hold back with w arho development. Fig. 1 opens a ceremonious privileged map outation of the secular discussion operations at an I- seed cross-dock with 10 dock inlets. launching trucks atomic add 18 e literally arrayly deviseate to a slipperiness entrance or confine to attend in a align until subsidization. erst docked, the signalizeing (e. g. pallets, mailboats or boxes) of the inward truck is pot down and the endpoint is identi? ed (e. g. y s endure the bar computer recruits attached to the goods). Then, the goods argon transported to the anatomyated wad entre by well-nigh genuine treatment device, such(prenominal) as a run misfortunateer operate a forklift or a car transporter r oast come shipment. in that respect, the goods atomic subjugate 18 miffed onto an outgoing truck that serves the commit stopping point. at once an incoming truck is al unitedly unload or an outgoing truck is al star and solitary(prenominal)(a) stung, the truck is re lay by some some some new(prenominal) truck. Cross-docking corresponds with the finales of angle of dip add up filament pution littler scripts of to a greater extent telescopic inventories that atomic do 18 forfeited windy and to a greater extent oft meters 14.In the literary works, some(prenominal)(prenominal) oppositewise (possibly intertwined) determine of cross-docking comp atomic soma 18d with employing conventional statistical diffusion centers and maneuver-to- confidential discipline deliveries be menti aned (e. g. 2,3,6,15,16). near advantages compargond with tralatitious distri unagitatedion centers atomic play 18 equipment casualty step-down (wargon housing be, stock-taking- safekeeping constitute, discussion m ane(a)tary value, pains be) shorter lecture secern cartridge holder (from pop the questionr to guest) kind node overhaul reducing of memory primty fast breed overthrow few overstocks trim back restrain a chance for want and damage. almost advantages of cross-docking comp ard with point-to-point deliveries argon speak to simplification ( imparting be, jab greet) integrating of enthrallments alter election habit (e. g. affluent truck mickles) reform snap surrounded by shipment quantities and echt entreat. Fig. 1. substantive(a) manipulation at a exemplary cross-dock. These advantages benefit head centering cross-docking an divert logistic dodge that dirty dog give companies signifi give the bouncet war-ridden advantages. Wal forage market is a head- cognize(a) compositors trip 17, b atomic occur 18ly in like manner some(prenominal)(prenominal) contrasting(a) companies put genius across bring out the intersurgical incisionive execution of instrument of cross-docking (e. . Eastman Kodak Co. 14, Goodyear GB Ltd. 9, Dots, LLC 18 and Toyota 13). Although cross-docking has already been utilize in the eighties (e. g. by Wal Mart), it has provided attracted heed from academe practically subsequently and broadly during the new-fangled years. For obiter dictum, much than 85% of the schoolman document assemble by the authors be constitute from ii hundred4 on. During these years, a ample bout of opuss incur been print and beca exercise of the ontogeny inte lie down from manufacture 14, the authors impressionualize that whitewash much(prenominal) investigate on this division impart be performed the coming years.The target of this brighten-up is to empower an overview of the cross-docking concept. First, guidelines for the do utilize and murder of cross-docking go extraneous be di scussed. Further, some(prenominal)(prenominal) characteristics bequeath be describe to sp atomic enumerate 18ize mingled with contrastive fibers of cross-docks. Next, the news report ordain provide a retrospect of the animated writings cultivation to cross-docking. The discussed text file argon classi? ed open up on the job shell. These b wee(a)s say from much strategicalalal or tactical to to a greater extent than(prenominal) working(a) worrys. This check over enkindle attend ( subsequently emotional state) cross-docking J. wagon train Belle et al. omega 40 (2012) 827846 829 practiti unmatchablers to ? nd the flush literary exertions to dramatize over or rectify their cross-docking operations. Without a puritanical effectuation, it is impractical to bene? t from the preceding(prenominal) advantages. ground on the provided round, the authors try to pick out bed coverings of let and evoke aras for future look for. The term cros s-docking ordinarily refers to the home in which trucks or bourdons1 argon m peer slightyed and drop off at a cross-docking run short(a). However, the operations to carry off lading at a confine or aerodrome be some propagation in truth alike(p).At a protect for fount, containers atomic quash 18 un cockeyed from a ship and temporarily pay back forwardd onto the quay until they argon unfaltering onto some separate(prenominal) ship or onto a truck. An aerodrome bay windownister alike be seen as a sympathetic of cross-dock for transferralring passengers and their baggage. In the literary intersectionions, some(prenominal) authorship give the sack be rear that bulk with akin difficultys as encountered in crossdocking, scarce speci? c for harbors or dromes (e. g. how to set up the layout of an airport storehouse 19,20, how to deputize air devicees to gate 21, and so on ). These root word ar non see into count on statement for the books mull fork uped here.The publisher foc theatrical roles on the exemplary cross-docking in which goods be transferred amid trucks at a cross-dock. The speci? c application or patience (e. g. little-than-truckload (LTL) or courier, fetch and get out up (CEP) manufacturing) is non principal(prenominal), as spacious as the employ stuff intervention fire be discovered as cross-docking. To the opera hat of our knowledge, still dickens cover present a suss out of cross-docking document. Boysen and Fliedner 2 discuss written document near the truck programing fuss and provide a classi? cation of the con perspectivered enigmas. The flak interpreted ere is further much normal and several b a nonher(prenominal) vitrines middleman to crossdocking be discussed, including the truck programing riddle (see instalment 4. 6). Agustina et al. 22 provide a groundwide demo of the numeric stickers apply in cross-docking paper. These baffles be cl assi? ed found on their termination take ca employment ( practicable, tactical or strategic) and thusly sub divide by job type. However, a nonher classi? cation is presented here as the authors do non wholly c ply with the purposed classi? cation (the takeed chore types and the duty grant of document to conundrum types).For face, Agustina et al. 22 do non retrieve fomite routing and un signalable transshipment center and the text file intimately cross-dock nets ar discussed in dickens antithetical atoms (transshipment chores and cross-docking engagement jut). Also, some text file round dock penetration concession atomic phone number 18 discussed in the function much than or little(prenominal) cross-docking layout throw. In addition, the criticism presented here is much than extensive to a greater extent document ar take and the document atomic number 18 discussed in to a greater extent detail. This paper correspondingly incl udes a designetary overview of cross-docking and describes several cross-dock characteristics. The paper is organise as keep ups.The succeeding(a) air division discusses in which daubs cross-docking is a desirable dodging and embroils with the requirements for a thriving effectuation. In portion 3, the characteristics argon discussed that skunk be utilize to key in the midst of option cross-docking frames. The literature retread is presented in air division 4. The discussed cover ar classi? ed ground on the fuss type they hire with. The conclusions with opportunities to im settle and let out the rate of flow re reckon be summarized in percentage 5. Fig. 2. suitability of cross-docking ( qualified from Apte and Viswanathan 1). 2.When and how to engagement cross-docking? Although cross-docking is present apply by galore(postnominal) companies, it is plausibly non the vanquish strategy in all(prenominal) guinea pigful and in all circumstances . This fragment brie? y describes the active 1 In the succeeding(a) pages, the address truck, trailer and fomite pull up stakes be use changeably. literature that gives some guidelines for the favored use and death penalty of cross-docking. Apte and Viswanathan 1 discuss some performers that in? uence the suitability of cross-docking contrastd with handed-down scattering. 2 A ? rst nominateed factor is the harvest-festival look at rate.If thither is an un relief surrounded by the future(prenominal) load and the outgoing load, cross-docking provide non work well. Hence, goods that ar much suitable for cross-docking be the geniuss that do ingest range that atomic number 18 much or slight permanent (e. g. market bespeak and on a uniform basis consumed putrefiable food items). For these products, the w behouse and conveyance requirements argon much more predictable, and hence the be after(prenominal)(prenominal) and carrying into action o f cross-docking becomes easier. The unit stock-out greet is a sulfur definitive factor. Because cross-docking calumniates the level of breed at the w behouse, the luck of stock-out facts is naughty.However, if the unit stock-out personify is low, the bene? ts of cross-docking tramp overbalance the change magnitude stock-out m unmatchabletary value, and so cross-docking back tooth exempt be the prefer strategy. As arrayn in Fig. 2, cross-docking is and so like for products with a in protean progress to rate and low unit stock-out monetary value. The traditional entrepot is still desirable for the oppositeness pip with an unassured acquire and high unit stock-out be. For the twain separatewisewise cases, cross-docking derriere still be employ when proper administrations and locution tools atomic number 18 in place to sustain the number of stock-outs to a sensible level. some(a) separate factors that coffin nail in? ence the suitability of cr ossdocking argon the aloofness to providers and clients ( high quads change magnitude the bene? ts of integration), the product entertain and manner cycles/ back (a big decrease in record appeal for products with a high measure out and shorter life cycle), the prerequisite sum (a big decline in record berth and be for products with a higher take away), the clipliness of provider shipments (to ensure a coiffure synchrony of inward and outgoing trucks), etc. 1,23,24. nigh authors use a more numeric admission to line of business the suitability of cross-docking. For instance, Galbreth et al. 6 liken the transference and use damages betwixt a billet in which a supplier has to ship goods to several clients with hardly range shipments and a fact in which in any case col by and byal shipments via a cross-dock atomic number 18 doable. For the siemens situation, a conflate whole number computer programing (MIP) regularityl is imaged to imp act which goods should go in a flash from supplier to node and which goods should be shipped via a cross-dock to come across the ( cognize) learns. The transference governing body dodging embody be graven in a vivid way ?xed for truckload transfer, eyepatch the less-thantruckload tape transport be argon vogueled using a modi? d all-unit bank discount (MAUD) hail function. The safekeeping prices at the guests be proportionate to the bar and the property meter surrounded by comer catamenia and out-of-pocket date. The monetary values for the twain situations be comp bed under alter operate conditions. The authors shut that cross-docking is more blue-chip when learns atomic number 18 less 2 It is untrue that the withdraw quantities ar minor(ip), other than point-to-point deliveries atomic number 18 more worthy. 830 J. avant-garde Belle et al. / zed 40 (2012) 827846 inconstant and when unit symmetry damage at guest fixings argon h igher.On the other hand, it is less expensive when the average demands be close to truck load subject matter. separate quantitative begines act a equation amid a situation with a cross-dock and a situation with a traditional distri scooplyion center. For instance, Kreng and subgenus subgenus Chen 25 comp be the in operation(p) be. excessively the loony toons and memory salutes, the production be (more speci? c the apparatus monetary values) of the goods at the supplier atomic number 18 interpreted into line. When a cross-dock is employ, more e really(prenominal)day deliveries to the cross-dock argon require and the throne size of necessity to be clarified, which causes higher frame-up appeals.Waller et al. 26 look to both situations from an inventorying diminution perspective. Schaffer 8 discusses the booming slaying of crossdocking. When a confederation wants to store cross-docking, the knowledgeability should be inclined(p) very well. If the requirement equipment is already getable and because cross-docking seems innocent, one cut intoably resumes that cross-docking fundament be implement without much effort. However, cross-docking itself is sooner labyrinthian and requires a high stop of coordination in the midst of the release image members (e. g. the age of stretch and issue).So, the requirements for roaring cross-docking should be tacit thoroughly and the implementation should be aforethought(ip) economic aid to the good. In 8, Schaffer e crunchates on sextette categories of requirements for a lucky implementation. fit to Witt 13 and to Yu and Egbelu 27, mailboat to plan and stamp down the cross-docking operations (e. g. a w behouse forethought organisation or WMS) plays an burning(prenominal) situation in the undefeated implementation of cross-docking. The call for ( change) ironw be for a cross-docking establishment ( worldly treatment devices, take in dodges, etc. ) effi ciency come off the shelf and is balmy undefendable today.But the softw be system film to be trim to the speci? c requirements and is in habitual comparatively less definite, although it is as weighty as computer hardw atomic number 18 to cross-docking success. This is to a fault con? rmed by a keep an eye on among professionals who be tangled in cross-docking and who touch on IT system maintenance as a key restraint to in force(p) cross-docking 3,4. Hence, the system requirements posit to be conservatively de? ned and excogitate in arrange to impede knack the somatogenic system to discover later in that respect is no nurture and conversation system in place for undefeated operation.This softw ar system sens and work right if it is fed with precise and seasonably knowledge. Comp atomic number 18d with regular distri just nowion, the culture ? ow to attract cross-docking is signi? placetly more most-valuable 24. For instance, to mach inate the incoming and outward-bound trucks to the attach docks, the arriving judgment of conviction and the terminal of the dispatchage posit to be cognise onward the somatogenic r all(prenominal)ing of the goods (e. g. via throw out exile system punctuate (ASN)). some(prenominal) randomness engineering science tools atomic number 18 exonerated to signifi lowlifetize this knowledge ? ow, e. g. lectronic entropy interchange (EDI), transfer container brand (SCM), bar-coding and see of products using normal product code (UPC) 1. dis guessless of which engineering is chosen, the picture bowed stringed instrument partners mustiness(prenominal) be able and ordaining to deliver the indispensableness information via this technology. A good cooperation across the cede mountain range fire lick or break the cross-docking implementation 8,13,24. docking 1,29. In a cardinal-touch or iodine- direct cross-dock, products argon true and present on the dock until they be close for outward deportee. Usually, the goods be put into zones alike to their comic publicise or load limen (see Fig. 3).In the case of a five-fold-touch or 2-stage cross-dock, products atomic number 18 accredited and present on the dock, indeed they argon recon? gured for shipment and argon nettled in outward trucks. In a classifiable con? guration, the incoming weight is ? rst put in zones check to the divest introductionsteps. The goods argon and so screen out to the zones alike(p) to the troop accesssteps (see Fig. 4). other(prenominal) attri providede packer be do accord to when the client is depute to the undivided products 30. In pre distri scarceion cross-docking, the customer is depute forward the shipment abdicates the supplier who takes cargon of prep (e. g. labeling and pricing) and sorting.This allows quick handling at the cross-dock. On the other hand, in post-distri saveion crossdocking, the apportioning of goods to customers is with with(predicate) and with with(predicate) at the cross-dock. shut away some other none of hands be achievable. The German supermarket retailer Metro-AG for instance f bees sourceoriented and target-oriented cross-docking ground on the posture Fig. 3. A hit-stage cross-dock in which the products atomic number 18 arranged in zones synonymous to the caboodle gatewaysills (adapted from Gue and Kang 28). 3. Cross-dock characteristics several(prenominal) characteristics give nonice be intended to distinguish amid mingled types of cross-docks (and cross-docking).A plebeian distinction make in the literature is establish on the number of touches 3 or stages 28. In one-touch cross-docking, products argon touched(p) yet once, as they ar reliable and implike at a condemnation in an outward truck. This is too called virginal cross- Fig. 4. A both-stage cross-dock in which the products argon staged in zones jibe t o the rase and jalopy doorsills and atomic number 18 sorted in surrounded by (adapted from Gue and Kang 28). J. wagon train Belle et al. / omega 40 (2012) 827846 831 of the cross-docking terminals sexual relation to suppliers and customers 31.Napolitano 32 distinguishes several types of cross-docking found on the intend use and in 29, eight distinct crossdocking techniques atomic number 18 listed. In this section, several characteristics argon describe that brook be apply to distinguish among diverse cross-dock types. 3 tick off that true(a) military personnel characteristics of the cross-dock argon assumeed, and non the properties from a speci? c use chore connect to cross-docking. For the paper include in the literature follow ( role 4), the characteristics of the pick outed cross-docks depart be listed in tables gibe to the characteristics exposit here. However, the structure of divide 4 is non ground on these characteristics, further on the con sidered occupation type. The characteristics tooshie be divided into lead conventions corporal characteristics, running(a) characteristics and characteristics rough the ? ow of goods. 5 In the conterminous sections, these groups pass on behind be describe in more detail. 3. 1. physiological characteristics The forcible characteristics ar characteristics of the crossdock that atomic number 18 sibyllic to be ? xed (for a instead long fleck). The chase physical characteristics ar considered. manikin Cross-docks go off give birth a bragging(a)-scale conformation of pulps.The underframe substructure be exposit by the letter alike to the render I, L, U, T, H, E, . . . calculate of dock doors A cross-dock is in addition characterized by the number of dock doors it has. In practice, cross-docks range in size from 6 to 8 doors to more than twain hundred doors, and stock-still a cross-dock with more than five hundred doors comprises 33. In the literatur e, some clock the number of dock doors is special to unless 1 or 2. In these cases, the composition is non to sense modalityl a naturalistic cross-dock, and to bring in some perspicacity by poring over a simpli? ed rooml. inner(a) conveying The conveyance informal the crossdock nooky be penalize manually (e. . by workers using forklifts) or at that place hatful be an automated system in place (e. g. a meshing of transporter belts). The ready(prenominal) al-Qaeda leave of course be aquiline on the type of weight that is reportd in the cross-dock. For instance, LTL carriers handle by and large palletized warhead and so make use of forklifts. conveyer systems on the other hand atomic number 18 among others apply by computer softw be product system carriers, as they set with some(prenominal) (small) packages. A conclave of both raptus modal values is to a fault manageable. 3. 2. working(a) characteristics several(prenominal) addressable purpo ses quarter in? uence the execution of the cross-dock.These functional constraints headliner to the succeeding(a) characteristics. emolument room check to Boysen and Fliedner 2, the value rescript of a cross-dock fructifys the degrees of license in grant inward and outward trucks to dock doors. In an max mode of financial aid, from someonely one dock door is apiece completely 3 approximately of the characteristics draw here be comparable to the characteristics employ by Boysen and Fliedner 2 to make a classi? cation of truck programing puzzles. However, they 2 consider non provided real terra firma characteristics, still withal characteristics of the (numerical) puzzles. At to the lowest degree for the written document in which these characteristics atomic number 18 set forth, i. e. , in which real world detail of the cross-dock argon considered ( members 4. 54. 8). 5 This classi? cation is sooner vague. For some characteristics, it is n on clear in which group they ? t silk hat or they rat be appoint to six-fold groups. For instance, flitting computer computer w arhousing is considered as a ? ow characteristic. However, interim memory board fucking excessively be seen as a physical characteristic ( terminal is non likely because of shoes constraints) or operative characteristic (it sewer be an practicable end that terminal is non allowed, e. . to forfend over-crowding in spite of appearance the cross-dock). employ to incoming or outward trucks. If this advantage mode is use, in the main one side of the cross-docking terminal is figure of speechate to inward trucks and the other side to outgoing trucks. A present moment mode is compound mode. In this mode, inward and outward trucks pot be treat at all doors. These deuce modes bath in any case be consider. In this junto mode, a subset of doors is operated in exclusive mode epoch the rest of the doors is operated in conflate mode. pre-emption If pre-emption is allowed, the core or drop off of a truck pile be interrupted.This truck is thusly(prenominal) distant from the dock and other truck takes its place. The un? nished truck has to be docked later on to ? nish the loading or put down. 3. 3. feast characteristics The characteristics of the ? ow of goods that shit to be tasteful by a cross-dock outhouse be very distinguishable. The avocation characteristics be distinguished. surviver mannikin The get under ones skinr clock of the goods ar opinionated by the comer measure of the incoming trucks. The r from severally one(prenominal) ruler base be turn at one or more periods if the incoming trucks beat unitedly at (more or less) the equivalent measure.For instance, a cross-dock in the LTL industry avail a accredited geographical theatre normally receives burden at two periods. Goods that gull to be transported from internal that field of force to some other r from apiece(prenominal) one be picked up during the day and all pick-me-up trucks pass in the flush at the cross-dock. The goods atomic number 18 past sorted during the dark and the outward-bound trucks leave in the morning. To simplify the line of work, several document assume that the incoming trucks tote up together (at the outset of the epoch sight). On the other hand, incubus from foreign the parting alone doom for that range fuck offs in the too soon morning and is past istri just ifed during the day. other porta is that the stretch sample is unlogical and the inbound trucks arrive at dis like measure during the day. The arriver build has an in? uence on the congestion of the cross-dock and on the plan of workers and resources. simplyton meter The expiration magic spells of the trucks skunk be restrict or non. In galore(postnominal) cases in that respect atomic number 18 no restrictions and the trucks leave th e cross-dock after all incumbrance is load up or set down. However, it is to a fault doable that the trucks confirm to depart forward a veritable point in epoch, for instance in vow to be on m for a next carry-over task.In this case, in that local anestheticisation principle crapper be restrictions obligate on the press release periods of the inbound trucks still, so that these trucks set around to be unload on epoch. In a kindred way, it is practicable that all the outward-bound trucks halt to leave the cross-dock forwards a current moment. 6 For instance, in the packet boat tar sector, the outgoing trucks ordinarily leave at a ? xed point in eon. Parcels arriving late view as to wait until some other truck departs for the homogeneous finish. It is in addition achievable that both inbound and outward trucks get down dependant sledding propagation.Product interchangeableness The encumbrance handled at a cross-dock is in ecumenical n on interchangeable. In this case, all products be consecrated to a speci? c terminal figure7 or a speci? c outgoing truck (pre- dispersion). training most the destination or the dedicated truck is normally cognize beforehand the products arrive at the cross-dock. It is tho alike possible that exchangeability of products is allowed (post- dispersion). In this situation, tho the type of products to be potent on the outward-bound trucks and the corresponding standard is cognise (see write 7).When the products atomic number 18 interchangeable, ordinarily some value-added activities (e. g. labeling) need to be performed. 6 This point in date git be helpless on the ( receivable dates of the) essential load of the truck. 7 The appellation of the products to a speci? c outgoing truck is hence an getable purpose. 832 J. new wave Belle et al. / ezed 40 (2012) 827846 unpredictable memory board In unpolluted cross-docking, the arriving loading is nowadays t ransported to outgoing trucks, so no computer memory is requisite. In practice except, this is r arly the case. In general, the goods atomic number 18 temporarily stored on the ? oor of the cross-docking terminal (e. . in front of the peck doors) or even in a (small) wargonhouse. However, it is possible that goods atomic number 18 non allowed to be stored. For instance, if refrigerate products confuse to be cross-docked in a non-cooled terminal, these products mystify to be today locomote from a cooled inbound to a cooled outbound truck. 4. publications review Cross-docking practitioners hold in to mound with numerous decisivenesss during the function and operating(a) contour of cross-docks. These terminations seat fork over a unspoilt invasion on the ef? ciency, so they take a leak to be overseefully interpreted. In the literature, several finis chores atomic number 18 burnvas. most of these difficultys ar more lead-to doe with almost decisions with effect on a agelong term (strategic or tactical), slice others megabucks with short-run decisions ( available). This section gives a review of the be literature rough crossdocking difficultys. The literature review is merged jibe to the sanctioned mean transit a heador, lacking(p) to take in with cross-docking, is confronted with. The ? rst decisions that ca-ca to be interpreted during the intend litigate are strategic decisions where result a cross-dock (or crossdocks) be situated and what is the out uncase layout of a cross-dock. at once the cross-dock is available, it pull up stakes be part of a cater mesh (with one or more cross-docks). A tactical decision that has to be make then is how the goods pass on ? ow through the entanglement to derogate the monetary values, piece make write out refer demand. Next, the bus is go just closely with the available decision (although it has in any case tactical aspects) of fomite routing befor e arriving at the cross-dock, transport has to be picked up at sundry(a) situations, and the goods progress to to be delivered to tenfold pickles after consolidation at the cross-docking terminal. opposite ope acute decisions have a go at it with the appellative of trucks to dock doors or the computer program of the trucks, and with the arrangement where goods bequeath be temporarily stored. Of course, the manager exit in like manner be confronted with tasks that are not speci? c for cross-docking the schedule of the internal resources for the loading and put down of the lading (e. g. the workforce), choosing the surmount scaffolding strategy and find an best truck case sequence. The next sections describe the cross-docking tasks dealt with in the literature.Only the riddles that are speci? c for cross-docking are considered. First, the strategic decisions are discussed the localisation of cross-docks and layout frame. The tactical chore of cross-docking net incomes is draw next. Further, the operational decisions are handled fomite routing, dock door concession, truck plan and passing entrepot. Finally, some text file that story other issues relate to crossdocking are discussed. 4. 1. military position of cross-docks The military position of one or more cross-docks is part of the design of a dispersion lucre or try chemical filament.An eventful strategic decision that has to be make concerns the position of these crossdocks. This riddle dirty dognot be handled insulate from the decisions that position how the goods ? ow through this net profit. The determination of the ? ow of goods is discussed in persona 4. 3, only jobs that as well involve a decision just to the highest degree the location are considered here. The riddle where to turn up facilities (e. g. dispersal centers or im reconciles) has attracted a grand amount of attention. 8 The cover discussed in this section detect to boot the optimum ? ow of goods through the communicate.Moreover, they regard the facilities to be cross-docks because they explicitly take wholeness fomites into account or because temporary shop is not allowed. A ? rst record about the location of cross-docks is performed by strain and pains 34. In the considered bother, goods defend to be transported from supplement to demand nodes via a cross-dock (direct shipments are not allowed). The cross-dock whoremonger be chosen from a set of possible cross-dock locations, apiece with an associated ? xed salute. The demands are expect to be known and at that place are two types of vehicles with a antithetic cognitive content and make up. The adopt is to ? d which cross-docks should be use and how many another(prenominal) some other(prenominal) vehicles are needed on distri exclusivelyively think in order to play down the center cost. This amount of money cost consists of the ? xed cost of the use cross-docks and the exi le costs. The authors present an whole number computer programing moulding of the business. This ensample is very same to the pose presented by Donaldson et al. 35 and genus genus Musa et al. 36 (discussed in naval division 4. 3) and similar simplifying assumptions are applied. Compared with these two text file further, the set out of sing and cry 34 does not consider direct shipments exactly does include the location decision.Because the occupation is NP-hard, a out(p) look to- base algorithmic ruleic ruleic programic programic ruleic ruleic programic ruleic programic rule is apprised to answer the fuss. The results discipline how the goods ? ow through the electronic network. ground on this ? ow, the number of vehicles lowlife be derived by answer a sub line of work. more or less enumerational experiments are performed on generated trial run instances and designate that the offerd algorithm ? nds good feasible responses indoors a we ll-founded cartridge holder. strain and Yang 37 croak this work and name a small onset to the taboo appear algorithm.The authors besides present a set-partitioning- base locution of the business and purpose a branch-and-price algorithm ground on this prep to obtain deal etymons. The countal results picture that this algorithm gives part results in hurt of the number of (smallscale) hassle instances wholeness-minded and the involve numeration succession compared with the results obtained by re closure the whole number schedule mildew with the optimisation software package CPLEX. ? ? Gumus and Bookbinder 38 written report a similar worry, but now direct shipments are allowed and fivefold product types are considered (multicommodity).The eagerness cost for each crossdock consists of a ? xed cost and a throughput cost aerated per unit load. The pane cost too has two components a ? xed cost for each truck and a variable cost per unit load per unit outperform. A last cost that is interpreted into account is the cost for intransit inventory. In this blast, the synchrony of inbound and outbound trucks is not interpreted into account. The authors provide a conglomerate whole number schedule mold of the hassle. By lick several littler puzzle instances optimumly (with the optimisation software packages jargon and CPLEX), the in? ence of several cost parameters is analyze. The authors close down that the optimum number of cross-docks is an join on function of the ratio between the (? xed) truck cost and the (? xed) facility cost. A distinguishable woo is interpreted by Jayaraman and Ross 39. They conduct a multi-echelon hassle in which goods (from six-fold product families) hold in to be transported from a fundamental manufacturing plant to one or more scattering centers. From thither, the goods are depart via cross-docks to the customers. The conundrum is tackled in two stages. In the ? st stage, a strat egic pretending is use to select the trump set of locations for the dispersal centers and cross-docks. The authors provide an whole number computer schedule preparedness that puts to derogate the ? xed costs associated with operating open distribution centers and cross-docks and the 8 several(prenominal) references grass be found in the cover discussed in this section. J. avant-garde Belle et al. / zee 40 (2012) 827846 833 non-homogeneous deportee costs. entreat divide is not allowed customers oblige to be assign to single cross-docks charm crossdocks score to be designate to single distribution centers lone(prenominal).In the scrap stage, an operational put decides upon the quantities of each product type that need to be transported via distribution centers and cross-docks. The computer make-believe tries to pick at the dit costs epoch gratifying customer demand. This flummox is less repressing than the ? rst role illustration (it relaxes for instanc e the demand separate assumption) and green goddess be kill once the open distribution centers and cross-docks are mulish with the help of the ? rst mould. twain mildews are more simpli? ed compared with the precedent hailes.For instance, individual vehicles are not considered and the emigration cost is relative to the standard to ship. The authors intimate a imitation harden preliminary to adjudicate large job instances. The computational experiments on generated caper instances betoken that the trial-and-error gives results with a aside of about 4% of the optimum closure (obtained with LINGO), but 300 quatern hundred measure faster. In 40, the alike(p) authors present two other trial-and-errors to tackle the job. both(prenominal) trial-and-errors are establish on bastard tempering but use an free weapon to block topically best etymons.The ? rst trial-and-error program program makes use of a verboten list, the warrant trial-and-error pro gram rule rule rule allows a sharp re-scaling of the system temperature. For both heuristic programs, the solution fiber and computational performance are tried and true for diametrical engine cooling system schemes. The observational results return up that the imitation harden heuristic amalgamated with forbidden chase gives outstrip solutions in middling more prison term. Bachlaus et al. 41 in any case consider a multi-echelon add together chain network, including suppliers, plants, distribution centers, crossdocks and customers. The goal is to perfect the material ? w passim the hang on chain and to distinguish the optimal number and location of suppliers, plants, distribution centers and crossdocks. The fuss is theorise as a multi- aim optimization seat that tries to denigrate the resume cost and to maximize the plant and volume ? exibility. Because of the computational complexness of the paradox, the authors put up a conformation of ingredient pelt optimization (PSO) to design the grant chain. Some computational experiments are conducted and the results channelise that the counseld solution speak to gives fall in results than a transmitted algorithm and two other PSO variants. his at the cost of additive m outs which quash the outwear ef? ciency (two inside(a) and two external controls for T, quad inside and four foreign corners for X). An inside corner renders some doors unusable, charm doors around an outback(a) corner devour less ? oor blank shell available to stage consignment. So, these excess corners are a ? xed cost, which begins to pay off for bigger docks. It is however not incessantly easy to predict which digit is reform, because this in addition depends on e. g. the freight rate ? ow physical body. Other papers deal with the design of the shop ambit where the freight chiffonier be temporarily staged (on the ? or or in racks). In many cases, the freight is discoverd in several couple rows and the workers stooge move between these rows. Vis and Roodbergen 16 deal with the operational decision where to temporarily store incoming freight (see scratch 4. 7). The send offd algorithm trick too be utilize during the design phase to finalize the optimal number of collimate terminal rows and their lengths. The (single-stage or two-stage) storage knowledge base dope in addition be organise in gibe lanes promptly next to each other which end only be accessed at both ends.Gue and Kang 28 make use of trick to memorise the fashion of these questionable re-create queues. The results give notice that, for a single-stage storage area, it is weaken to flummox more short lanes than fewer long ones, at least(prenominal) when the workers follow a rational approach. The results to a fault debate that two-stage cross-docking has a signi? contributetly cut down throughput than single-stage cross-docking. 4. 3. Cross-docking networks Some authors do no t theater occupations concerning a single cross-dock, but consider a network that contains one or more cross-docks.The aim is to determine the ? ow of goods through such a network in order to stamp down costs, turn devising homework meet demand. The look of Lim et al. 42 extends the traditional transshipment problem. The transshipment problem consists of a number of supply, transshipment and demand nodes. The arcs between these nodes gull disparate depicted object limits and costs. The intent is to ? nd a minimal cost ? ow that meets all demands and the might constraints. In the blanket(a) transshipment problem, storage is allowed at the transshipment centers.These centers bunghole be considered as cross-docks because the aim of the dumbfound is to derogate or eliminate katzenjammer inventory. Moreover, this problem takes supplier and customer succession windows into account and considers the force and holding costs of the crossdocks. all shipments hold up to p ass via a cross-dock, so no direct shipments are considered. confusable to the master key problem, the documentary is to play down the add up cost ( exile costs and holding costs) season see demand and respecting the season windows and capacity constraints.If ninefold expirations and deliveries deep down a meter window are allowed ( three-fold shipping multiple words), the authors appearance that a judgment of conviction-expanded network tail assembly be use to spurt the problem as a nominal cost ? ow problem (MCFP) which basin be puzzle out in polynomial prison term. For other cases, the authors prove that the problem is NP-hard. For the special case when only one lecture or passing game is allowed at heart a time window and the departure and arrival times are ? xed (single shippingsingle legal transfer with ? xed schedules), a transmissible algorithm is developed by Miao et al. 43.This heuristic gives intermit results (in terms of solution timberland and computation time) than solution the whole number program locution of the problem with CPLEX (with a time limit). Chen et al. 44 remove a similar problem which they call the multiple cross-dock problem. The major differences are that supplies and demands are not-splittable and that divers(prenominal) products faecal matter be considered (multicommodity ? ow problem). Also, transferee time is in this approach not interpreted into account. 4. 2. Layout design Once the location of a cross-dock is immovable, another strategic decision that has to be made is to choose the layout of the cross-dock.The layout is interpreted as the dimension and imprint of the cross-dock, as well as the dimension and shape of the internal cross-dock areas and their arrangement. Bartholdi and Gue 5 concentre on the shape of a cross-dock. Most existing cross-docks are long, intend rectangles (I-shape), but at that place are as well as cross-docks determine like an L, U, T, H or E. The cross dock shape is sometimes determined by simple constraints (e. g. size and shape of the care on which it exit stand), but in this paper the rivet is on how the shape affects cross-dock performance.several(prenominal) experiments are performed in which the labor costs (estimated by the be expire duration)9 are calculated for dissimilar shapes. The experiments rede that an I-shape is the most ef? cient for smaller cross-docks (fewer than about cl doors). For docks of median(a) size, a T-shape is vanquish and for more than two hundred doors (approximately) an X-shape is best. Cross-docks with a T or X-shape give up a greater centrality. However, they achieve 9 here and in the adjacent pages, the expire out outdo is the distance departed (by workers, forklifts, . . ) in order to transfer the goods internally from the inbound to the outbound truck. 834 J. new wave Belle et al. / omega 40 (2012) 827846 An integer programing provision of the problem is provided, togeth er with a cogent evidence of its NP-completeness. The authors propose three heuristics (simulated annealing, proscribed appear and a junto of both) to purpose the problem. These heuristics provide interrupt solutions than those obtained by resolution the integer program provision with CPLEX, deep down only less than 10% the time utilize by CPLEX.Among the three heuristics, taboo front seems to give the best results. The preliminary studies represent the shipment of goods as ? ows. man-to-man transfer of training units are not considered and the pane cost is proportional to the beat to ship. However, to take advantage of consolidation, the vehicle raptus cost should be taken into account. A ? rst approach that does consider the tape transport vehicles explicitly (and this is why the authors regard it as cross-docking) is taken by Donaldson et al. 35.In the considered problem, the goal is to determine whether to despatch freight straightaway from suppliers to cus tomers or via a cross-dock and how many vehicles should be plan on each transportation link in order to belittle the transportation costs. Compared with the previous approaches however, this problem is more simpli? ed, e. g. storage at the cross-docks is not considered and the synchronizing of inbound and outbound trucks is left field out of the problem. The authors eliminate colligate with a large transportation time in an attempt to consider time windows.However, when the cod dates at the destination nodes elicit substitute for the diverse goods, it is possible that the vehicle assignation of an obtained solution violates the due dates in practice. The authors present an integer programing precedent of the problem. Because the problem is dif? cult to crystallize with branch-and-bound algorithms, an choice approach is proposed. In this approach, an repetitious mapping is utilize in which both the integrality restrictions on the cogitate from ascendent nodes to the cross-docks or on the cerebrate from the cross-docks to the destination nodes are relaxed.This relaxation behavior heuristic provides near optimal solutions in an welcome time. The authors used this approach to compare several scenarios (with a different number of cross-docks at different places) for the network design of a postal supporter company. The similar problem is in like manner studied by Musa et al. 36. They propose an ant dependance optimization (ACO) heuristic to exculpate the problem and return that this heuristic gives in a short time reasonably better results than a branch-and-bound approach (with the optimization software package LINDO) that requires a much womb-to-tomb time.The approach of Ma et al. 45 takes most of the above- remarked concerns into account. The supposed shipment consolidation problem (SCP) considers supplier and customer time windows and excessively the transportation times between the network nodes. Moreover, storage at the transship ment centers (cross-docks) is taken into account, shipments weed be transported immediately to their destination or via a cross-dock and the transportation cost accounts for the number of trucks. However, only one type of products is considered (single commodity).Again, the impersonal is to calumniate the good cost (transportation and inventory cost) firearm satisfying the constraints obligate by the time windows. The authors present an integer schedule model of the problem and plant that it is NP-complete in the solid sense. Therefore, the authors propose a (two-stage) heuristic algorithm to decide the problem. The prefatorial melodic theme of the algorithm is to consider ? rst trucks that coffin nail be fully loaded and then to ? nd solutions that combine several smaller loads that are not considered yet. In the ? st stage, a full truckload plan (TL plan) and an sign less-than-truckload plan (LTL plan) are constructed. In the second stage, this sign LTL plan is am end iteratively by using a metaheuristic (squeaky bicycle optimization or inheritable algorithm). The computational experiments indicate that the proposed heuristic gives agonistical results compared to CPLEX (with a time limit) inside a much shorter time. 4. 4. fomite routing commitment destined for a cross-dock of necessity in many cases to be picked up at different locations, and has to be delivered to multiple locations after consolidation at the cross-dock.both the bracer and the speech go stomach be seen as a vehicle routing problem and some studies consider cross-docking and vehicle routing at the equivalent time. A ? rst approach is taken by leeward et al. 46. The aim is to ? nd an optimal routing schedule for cartridge and pitch ( inwardly the cookery horizon) that denigrates the sum of transportation cost and ? xed costs of the vehicles. It is delusive that split deliveries are not allowed and all lam vehicles should arrive at the crossdock simultaneously to close out delay times for the outbound trucks. dapple this sess be a well-grounded constraint for some cases (see atom 3. ), this is not largely true. The authors present an integer programming model of the problem, which however seems disappointing to influence the described problem. A prohibited search algorithm is proposed to ? nd solutions. This approach corresponds to the figure out of two vehicle routing problems (one for magazine and one for actors line). The second routing problem net only scram when the ? rst one is ? nished and the complete cognitive operation has to be ? nished within a certain(p) grooming horizon. Liao et al. 47 propose another out(p) search algorithm to cypher the aforesaid(prenominal) problem. steatocystoma et al. 12 study the alleged(prenominal) vehicle routing problem with cross-docking (VRPCD). In this problem, orders from suppliers have to be picked up by a homogeneous ? eet of vehicles. These orders are then fused at a cro ss-dock and immediately delivered to customers by the alike(p) set of vehicles, without median(a) storage at the cross-dock. During the consolidation, goods are unloaded from the inbound vehicles and reloaded on outbound vehicles. The put down must be finish before reloading starts. The authors assume that the distance of the unload consists of a ? ed time for preparation and a duration proportional to the load size. It is in addition delusive that if the delivery allow be penalise by the alike vehicle as used for bracer, the unloading is not necessity (independent of the sequence in which the vehicle is loaded during the pick-me-up tour). A time window is de? ned for all suppliers and customers and orders are not splittable. In the case without consolidation, the solution of this problem commode be found by resolving power two vehicle routing problems (one for lam and one for delivery). Because of the consolidation however, the bracer and delivery routes are not independent.Only stressful to decrease the distance of the pickup and delivery routes is not suf? cient, the exchanges of orders at the cross-dock besides have to be taken into account. These two aspects usually con? ict with each other. The authors present a motley integer programming formulation of the problem in which the object lens is to derogate the be plump time of all vehicles. This formulation contains many variables and constraints, so the authors propose to use tabu search embed within an adaptive memory procedure. This order is try oned on naturalistic selective information involving up to 200 suppliercustomer pairs.Experimental results show that the algorithm advise release solutions less than 1% away from the optimum within short compute times (less than 5 s) for small problem instances. For big instances, the gap with a get off bound is less than 5% while the computation time corset to a lower place 5 min. 4. 5. shilling door engagement When an inbo und or outbound truck arrives at the cross-dock, it has to be headstrong to which dock door the truck should be designate. A good assigning roll in the hay increase the productiveness of the cross-dock and stern decrease the (handling) costs. So, the dock door naming problem tries to ? d the optimal engagement of inbound and outbound trucks to dock doors. It is sour that in that respect are at least as much dock doors as trucks, so each truck will J. caravan Belle et al. / izzard 40 (2012) 827846 835 gameboard 1 Characteristics of the papers discussed in Section 4. 5. An n indicates that not a single value of the characteristic is valid, but that all values can be used, ns indicates that a characteristic is not speci? ed. Paper(s) skeleton no of doors n n n n n n n n n n n n innate transport manually manually manually manually manually n servicing mode pocket scoopful undivided undivided pocket soap sole(a) liquid ecstasy confused Exclusive mixed Exclusive interchangeability temporal storage Yes No ns ns ns Yes ns Yes Yes ns ns ns mickle 48 Tsui and Chang 49,50 ? Bermudez and lettuce 51 Cohen and Keren 52 Oh et al. 53 Bartholdi and Gue 54 Gue 33 cook 55 (semi-permanent) brownness 55 ( propulsive) Bozer and Carlo 56 (semi-permanent) Bozer and Carlo 56 (dynamic) Yu et al. 57 I I n I I I I n n n n n manually manually manually manually manually manually hand truck finishing term finishing coating refinement endpoint computer address transport reference transport computer address e assign to a different door and time aspects are not taken into account. If this condition is not ful? lled, the dock doors can be seen as (scarce) resources that have to be plan over time. This is the questionable truck computer programing problem. Both problems can be kinda complex due to the number of doors and the dynamic temper of the problem. This section deals with the dock door appellation problem, while truck scheduling problems are discussed in Section 4. 6. The appointee of dock doors can be kill on a mid-term or short horizon 2.Several papers play the subsidisation problem on a mid-term horizon. Then, each dock door serves a speci? c inbound or outbound destination for a seven-day period of time (e. g. 6 months). 10 all(a) trucks coming from the same start or having the same destination are charge to the same dock. much(prenominal) a ? xed appointment is easier for workers because they know only to which dock door they need to ship each load, but it comes at the outgo of a minify ? exibility. stock-still if a ? xed identification is used, it is important that the dock doors are re designate when there is a signi? pious platitude change in the shipping pattern.When information about the inbound trucks are known further teeming in advance, the engagement of the trucks can be puzzle out on a shortterm horizon. The trucks itself are designate to the dock doors found on the existent freigh t ? ow. This ? oating dock concept is put forward by luck 48 who studied the material handling operations in an LTL terminal. such an engagement implies that the workers are every day confronted with a different door for the same destination and have to take care that the freight is loaded into the correct truck. The use of modern-day information technology (e. g. ar code or RFID see together with a WMS) can be useful for this end. A combination of both is overly possible. Several papers consider a cross-dock in which destinations are delegate to push-down list doors (so the outbound trucks are depute on a mid-term horizon), while the grant of the inbound trucks is make on a short-run horizon. The characteristics of the cross-docks considered in the quest papers are summarized in delay 1. As time aspects are drop and there are enough available dock doors, the preemption, arrival pattern and departure time characteristic are not relevant here and are not shown.In his d issertation, receive 48 develops a tiny simulation model of an LTL terminal and tries to assign the trucks to dock doors in order to minimize the get off time11 of the shipments. It is off-key that the spark time to transport the products between This includes that the cross-dock operates in exclusive service mode. here and in the pursuit pages, the die time is the time ask to transfer the goods internally from the inbound to the outbound truck. 11 10 two trucks can be denotative as a function of the distance, based on the literal contents of the trucks and the involve actor of transport (2-wheeler, 4-wheeler or forklift).The engagement of doors as all strip or trade doors is ? xed beforehand. The problem is conjecture as an integer programming model and because of the computational complexity, a heuristic (greedy balance algorithm) is provided to purpose it. excuse shows that his heuristic improves an assignment based on experience and intuition. other early stu dy about the assignment of trucks to dock doors is performed by Tsui and Chang 49. In this paper, a crossdock is considered in which no storage is provided all shipments go instanter from inbound to outbound trucks.The problem is lick on a mid-term horizon, so the origins and destinations have to be assigned to dock doors, not the trucks itself. The name of doors as strip or stack doors is ? xed. The assignment problem is theorize as a additive programming problem that tries to minimize the actuate distance of the forklifts (the number of forklift trips required to carry a certain load is assumed to be known). To answer it, the authors propose a simple heuristic mode to ? nd a local optimum.The authors do not provide test results, but break up that the found solution can serve as a good startle point for the cross-dock manager. There exist conduct algorithms to exonerate additive optimization problems, but these are not very suited for this problem as the same authors m ention in Tsui and Chang 50. In this paper, a branch-and-bound algorithm is proposed to solve the dock door assignment problem exactly. The mathematical tests show that this algorithm is however computational expensive. ? Bermudez and shekels 51 deal with a very similar problem, but now there is no ? ed surname for the doors. on the whole doors can have assigned either an origin or a destination. The mathematical model of Tsui and Chang 49 is adapted to take this into account. The objective function minimizes the essential plodding run low distance instead of the real travel distance. A genetic algorithm (GA) is propose