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X12 transaction guide · Transportation

EDI 421 Estimated Time of Arrival and Car Scheduling

The X12 document railroads use to exchange car scheduling and estimated time of arrival data with each other.

Sent by
Rail carrier
Received by
Connecting rail carrier
Standard
ANSI ASC X12

What is an EDI 421?

The EDI 421 Estimated Time of Arrival and Car Scheduling is the ANSI X12 transaction set that lets railroads exchange car scheduling and estimated time of arrival data between carriers.

Car scheduling plans each car's trip as a series of train connections, with an estimated arrival at the destination or the next interchange. Sharing these plans between railroads gives an end-to-end estimate for interline shipments, which shippers rely on for planning. Trip plans are recalculated when trains are delayed or cars miss connections. Shared estimates let each carrier see how the others' delays affect a car's arrival at destination.

How the EDI 421 worksDiagram of the EDI 421 Estimated Time of Arrival and Car Scheduling. Rail carrier sends it to connecting rail carrier. It usually starts the exchange. It is usually followed by 997. Inside the ISA, GS and ST envelopes, X12 release 008010 requires, in the heading: IS1 (Estimated Time of Arrival and Car Scheduling), N9 (Extended Reference Information) and IS2 (Scheduled Events). 2 optional loops are listed by their first segment.How the EDI 421 worksEstimated Time of Arrival and Car Scheduling: who sends it, where it fits and what the standard marks required1 WHERE IT FITSUSUALLY FOLLOWSStarts the exchangeEDI 421SENDERRail carrierRECEIVERConnecting rail carrier997 or 999 acknowledgment back, if the partners agreeUSUALLY FOLLOWED BY997FunctionalAcknowledgment2 WHAT X12 RELEASE 008010 REQUIRESInterchange: sender and receiver IDsISA … IEAFunctional group, ID code ISGS … GETransaction set 421ST … SEHEADINGIS1Estimated Time of Arrival and Car SchedulingN9Extended Reference InformationIS2Scheduled Events+ 2 optional loops, starting with:S1LH1Blue box: required loop. Optional loops are listed by the segment that starts them; when a loop is used, that first segment is required. Optional segmentsoutside loops are not drawn.Structure: required segments and loops in the X12 008010 listing for the 421. Your trading partner's implementation guide adds its own requirements.
How the EDI 421 worksDiagram of the EDI 421 Estimated Time of Arrival and Car Scheduling. Rail carrier sends it to connecting rail carrier. It usually starts the exchange. It is usually followed by 997. Inside the ISA, GS and ST envelopes, X12 release 008010 requires, in the heading: IS1 (Estimated Time of Arrival and Car Scheduling), N9 (Extended Reference Information) and IS2 (Scheduled Events). 2 optional loops are listed by their first segment.How the EDI 421 worksEstimated Time of Arrival and Car Scheduling:who sends it, where it fits and what thestandard marks required1 WHERE IT FITSUSUALLY FOLLOWSStarts the exchangeEDI 421SENDERRail carrierRECEIVERConnecting railcarrier997 or 999 acknowledgment back, if the partnersagreeUSUALLY FOLLOWED BY997Functional Acknowledgment2 WHAT X12 RELEASE 008010 REQUIRESInterchange: sender and receiver IDs (ISA… IEA)Functional group, ID code IS (GS … GE)Transaction set 421 (ST … SE)HEADINGIS1Estimated Time of Arrival andCar SchedulingN9Extended ReferenceInformationIS2Scheduled Events+ 2 optional loops, starting with:S1LH1Blue box: required loop. Optional loops are listedby the segment that starts them; when a loop isused, that first segment is required. Optionalsegments outside loops are not drawn.Structure: required segments and loops in the X12008010 listing for the 421. Your trading partner'simplementation guide adds its own requirements.

How to read this diagram: the top row shows who sends the 421, to whom, and which documents usually come before and after it. The lower part shows what X12 release 008010 itself requires: the envelopes around the 421 and the segments and loops the standard marks as required, area by area. Optional loops are listed by the segment that starts them rather than drawn in full. This is the standard's minimum, not a trading partner's requirement: each partner's implementation guide usually makes some optional loops mandatory, restricts the codes and may use a different release.

Expand diagram Download SVG

When it is used

  • Sharing trip plans for interline cars
  • Exchanging estimated arrival times at interchange
  • Updating estimates after delays

Where it fits in the document flow

This document 421 Estimated Time of Arrival and Car Scheduling
Usually followed by 997 Functional Acknowledgment

Structure

Mandatory segments in the 421 (X12 release 008010)

The segments X12 release 008010 marks as mandatory at their level, in order. Segments inside optional loops are needed only when the loop is used. This is the standard's requirement, not your trading partner's: each partner's implementation guide names the release it uses, adds the optional segments it requires and restricts the values. The requirement status comes from one published X12 reference listing and has not been checked against a second source.

  • ST
  • IS1
  • N9
  • IS2
  • S1
  • LH1
  • N1
  • SE

Practical example

The 421 in practice

A car of auto parts moves over two railroads to an assembly plant. The origin railroad sends the destination railroad a 421 with the car's trip plan and estimated arrival at interchange. The destination railroad adds its own schedule, giving the plant a reliable delivery estimate.

Implementation

Implementation considerations for the 421

  • Update estimates when trains are delayed.
  • Use car identification consistent with waybills and consists.
  • Combine estimates from each carrier for end-to-end visibility.
  • Measure actual arrivals against estimates.

How ECOM helps

Automate the 421 with ECOM

Industry

Trucking and Transportation

Load tenders, responses, status and freight invoices for carriers, brokers and shippers, integrated with the TMS.

Solution

Supply Chain Visibility

Track orders, shipments and invoices across partners and catch exceptions early.

Industry

Automotive

Schedules, ship notices, labels, self-billing and multi-plant routing for automotive suppliers.

More general questions about EDI are answered in the EDI FAQ.

Related transactions

Related transportation documents

All 80 transportation documents

Need help with the EDI 421?

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