Andrew Turnbull presents

The History of School Transportation in Mercer County, WV

Technical Information: Deciphering VINs


school bus


Thomas' rear-engined Type D buses of the 1980s aren't exactly common survivors. Making matters worse, Thomas' VIN system of the 1980s is almost inscrutable. No reference source is readily available, and the VIN system has no obviously-apparent structure or order beyond the bare minimum.


Positions 1-3 and 11: Manufacturer and assembly plant

1T7-1 Thomas, High Point, North Carolina (US)

Whether Thomas ever built complete buses at its Woodstock, Ontario satellite plant is anyone's guess.

Positions 4-8: Unknown

The meaning of these characters is an inscrutable fog. Position 4 is a letter, positions 5, 7, and 8 are digits, and position 6 can be either. None of the digits have an obvious connection to a verifiable specification, such as engine choice.

Position 9: Checksum

0-9 or X, calculated from the other digits.

Position 10: Model year

Thomas appears to have aimed for industry-typical September model year transitions in this timeframe.

B 1981
C 1982
D 1983
E 1984
F 1985
G 1986
H 1987
J 1988
K 1989
L 1990
M 1991

Positions 12-17: Production sequence

Not even this makes sense: Serials for buses of this era seem to be drawn out of a hat at random, with the numeric sequence neither resetting with each model year nor progressing continuously. Positions 12-14 are tied to positions 3-5 of the Thomas body identification number, which is equally inscrutable.


Finally, a bit of order to lend method to the mayhem! Thomas Built Buses changed to a more predictable and better-documented VIN format with the 1992 model year.


Positions 1-3 and 11: Manufacturer and assembly plant

For reasons that elude me, Thomas' manufacturer prefix is contingent upon the configuration of the product:

1T7-1 Thomas, High Point, North Carolina (US) Rear engine
1T8-1 Front engine

Position 4: Model

5 ER (1992-2001), HDX (2001-03)
8 EF (1995-2012), EFX (2013-)
9 ER (1992-95)
H ER (1997-2003)
Y ER (2001), HDX (2004-21)

Position 5: Wheelbase?

The fifth character of the VIN contains an alphabetic or numeric code allegedly linked to the wheelbase of the bus. However, there is little overlap between known documentation and the codes actually seen in VINs.

Position 6: Type

2 Non-school, high headroom
3 School, low headroom
4 School, high headroom
9 School, EFX

Position 7: Engine

A Diesel (Mercedes-Benz)
B I6 Diesel
C Diesel (Caterpillar)
D 6.7L I6 Diesel (Cummins)
E 8.9L I6 Diesel (Cummins)

Position 8: Brake system

1 Hydraulic
2 Air

Position 9: Checksum

0-9 or X, calculated from the other digits.

Position 10: Model year

Thomas Built Buses retained a September model year cutoff through the first half of the 1990s. From that point on, the calendar started creeping further and further forward. MY1998 began by May of the year before; MY2000 began by February. By MY2005, the cutoff had migrated two calendar years in advance. And that's where things stand today, although Thomas' model year schedule remains a wee less exaggerated than corporate parent Freightliner's.

N 19922022
P 1993
R 1994
S 1995
T 1996
V 1997
W 1998
X 1999
Y 2000
1 2001
2 2002
3 2003
4 2004
5 2005
6 2006
7 2007
8 2008
9 2009
A 2010
B 2011
C 2012
D 2013
E 2014
F 2015
G 2016
H 2017
J 2018
K 2019
L 2020
M 2021

Positions 12-17: Production sequence

With the advent of this format, Thomas Built serials advanced from an starting point of (approximately) 110000. Numbers proceeded continuously from year to year (with a tiny amount of numeric overlap between years due to production discrepancies), periodically skipping or backtracking as follows:

Serials hit 168000 a fourth time during the 2021 model year. Shockingly, this time around Thomas didn't shift the numbering when it happened.

This information applies to Thomas' Type D buses, and specifically those built on in-house chassis. Thomas' newer Type C buses are built on Freightliner chassis, and continue to use the Freightliner VIN format.

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