A seat supplier a short drive from an assembly plant receives a call-off listing the next vehicles on the line: body number, trim, colour, options. Within hours, the seats for exactly those cars must be built, loaded in that order and unloaded at the line-side station they feed. That is just in sequence logistics, the tightest delivery discipline in road freight, and the reason automotive logistics is planned in minutes rather than days.
JIT and JIS are often used as synonyms. They are not, and the difference decides how the transport has to be run.
JIT and JIS: the difference is order
Just in time (JIT) delivers the right part number in the right quantity when the line needs it. Parts arrive in batches, the plant holds a small buffer measured in hours of consumption, and operators pick from it. Fasteners, brackets, standard modules and most single-variant parts run this way.
Just in sequence (JIS) adds order. Parts arrive in the exact sequence of vehicles on the assembly line, so the operator takes the next item from the rack and fits it without selecting. It applies to bulky, variant-rich parts where holding every variant at the line is physically impossible: seats, cockpit modules, bumpers, door panels, complete wheels and wiring harnesses.
| JIT | JIS | |
|---|---|---|
| Promise | Quantity and time | Quantity, time and order |
| Trigger | Consumption forecast or kanban call-off | Build sequence, frozen at a defined point in production |
| Line-side stock | Hours | Minutes, often one rack |
| Typical parts | Standard and low-variant parts | High-variant, bulky modules |
| Failure mode | Shortage | Shortage or wrong order |
A JIS load that arrives on time with two racks swapped has failed as surely as one that arrives late.
Why automotive plants run on JIT and JIS
The reasons are physical before they are financial. A modern assembly line builds many variants on the same track, and the combinations of seat fabric, steering side, engine and option packs run into numbers no line-side area could stock. Space along the line is the scarcest resource in the plant, and every square metre given to stock is a metre not available for assembly.
The second reason is takt. The line advances at a fixed rhythm, and every station must have its part when the body arrives. Sequenced delivery removes the selection step from the operator’s cycle, which keeps the takt achievable and cuts fitting errors.
The third is capital and quality. Parts that move from supplier to line in hours tie up little working capital and are handled fewer times, which means less damage. The cost of that efficiency is fragility: with almost no buffer at the line, the transport leg becomes part of the production process.
The information flow is as strict as the physical one. Call-offs usually travel as EDI messages under VDA or Odette conventions, with DELJIT as the EDIFACT message for sequenced and just-in-time call-offs, often over OFTP2. Why that channel persists in automotive while other sectors move to APIs is covered in the guide to API vs EDI in road freight.
What a late truck costs
When a JIS delivery misses, the line does not wait politely. Depending on the part, the plant either stops the line or keeps building and sends vehicles without the part to an off-line rework area, where fitting it later costs far more labour than fitting it in sequence. Both outcomes are expensive, and carmakers’ supplier contracts typically pass the downtime cost back to the supplier responsible, who in turn looks to the carrier.
The cost does not stop at the charge-back. A missed sequence triggers emergency freight, overtime at the supplier, re-sequencing work and, after repeated failures, escalation of the supplier’s quality status, which brings extra inspection and management attention. None of that is visible on the freight invoice, which is why the transport cost of a JIS lane is almost irrelevant next to its reliability. How punctuality penalties are measured and calculated in retail and manufacturing more generally is set out in the guide to OTIF in road freight.
What JIT and JIS transport has to deliver
The requirements are concrete, and most of them sit with the carrier and the logistics provider rather than the supplier’s production.
- Time windows of minutes. Unloading at the plant is booked into fixed slots tied to the line’s consumption. Early is often as unwelcome as late, because there is no space to park the trailer.
- Sequence integrity. Racks are loaded in reverse order of consumption, scanned at loading and checked again at unloading, so a swap is caught before it reaches the line.
- Sequencing and consolidation centres. Suppliers based far from the plant feed a sequencing centre close to it, which holds a short buffer, builds the sequence and runs short-distance shuttles to the line. The long-haul leg into that centre then runs as JIT, with a wider window.
- Milk runs. For JIT parts from several nearby suppliers, one truck collects from each on a fixed route and timetable, which keeps frequency high and loads full.
- Shuttle cadence and contingency. High-frequency shuttles between sequencing centre and line, with a planned answer for a breakdown: a standby tractor, a spare loaded trailer or an agreed emergency route.
- Returnable rack loops. Sequenced parts travel in dedicated racks and special containers that must flow back to the supplier on the return leg. A shortage of empties stops sequencing as effectively as a late truck, so the return flow is planned and tracked with the same discipline as the full one.
- Clean handover data. Each shuttle carries a reference that ties the trailer to the sequence numbers inside it, so the plant can confirm at the gate which part of the build sequence has arrived.
Many European plants draw parts over long distances, including from supplier clusters in Czechia, Slovakia, Hungary and Poland, and those long-haul legs carry the most variability: borders, weather, driving-time limits and congestion around the destination.
How live ETAs, slot booking and exception alerts protect the line
On a JIS lane the useful question is not where the truck is, but whether it will make its slot, asked early enough to do something about it. Three capabilities answer it.
Predicted arrival against the slot. A predicted ETA compared continuously with the booked unloading window shows a shortfall while there is still time to act: release the buffer at the sequencing centre, dispatch a standby trailer or re-plan the shuttle cycle. The accuracy of that prediction is what makes it usable, and the method behind it is explained in the guide to machine-learning ETA accuracy.
Slots that move with reality. Time slot management software holds the unloading windows that carriers book against, and lets the plant swap or re-assign a slot when a truck is known to be late, instead of discovering it at the gate.
Exception alerts. An unplanned stop, a route deviation or a stalled border crossing raises an alert to the people who own the contingency, not just a dot on a map that somebody may or may not be watching.
Live position data across every carrier on the lane is the foundation, as set out in the guide to freight visibility. Without it, the line learns about a late truck when the rack is empty.
TrucksOnTheMap provides that layer: real-time visibility, ML-predicted ETAs with up to around 95% accuracy, AI exception alerts and time-slot management, integrating with the systems where call-offs are planned rather than replacing them. TrucksOnTheMap connects the supplier’s or manufacturer’s own invited carriers, with a typical go-live in about seven weeks and a strong focus on Central and Eastern European lanes.
