Trains – September 2019

THE CABLESS “B” UNIT locomo-

tive dates back to almost the

beginning of dieselization. Such

units were constructed to mate

with one or more cab-equipped

“A” units to form a high-horse-

power locomotive set designed

to replace steam locomotives.

The practice largely died out

with the dawn of the hood unit

in the 1950s, but Union Pacific

continued to purchase B units

in sizable quantities for years to

come for both freight and

passenger service.

In the cab unit era when

EMD’s E and F units and Alco’s

PA and FA locomotives were

prevalent, B units were common

in consists on freight and pas-

senger trains. But later, the flexi-

bility of having new locomotives

with cabs, along with the higher

horsepower prime movers used

by the builders at the time, con-

tributed to the decline of B units

across the U.S. This shift made

the UP’s purchases remarkable

in the industry.

The first Union Pacific B

units of the hood era were two

orders of EMD GP9Bs. That in-

cluded a 75-unit order built in

1954 and a 50-unit order built

in 1957. Fifteen of the 50 units

from the second GP9B order

were retrofitted with steam

generators by the railroad and

were used in passenger service

across the system.

Union Pacific’s second order

of B units was for EMD’s six-

axle SD24B with delivery be-

ginning in summer 1959. All

45 SD24Bs built were for

freight service only and lacked

steam generator equipment.

The SD24B was an exception in

UP’s cabless fleet where the

number of B units purchased

outnumbered the number of

cabbed A units bought. The

railroad acquired only 34 regu-

lar SD24s, including the four

demonstrator locomotives.

The third order of cabless

locomotives came in the early

Union Pacific’s B units

Once an important part of UP’s fleet, cabless units lost their appeal in the 1990s

UP B units

• 125 GP9B


• 40 GP30B


• 27 DD


• 45 SD24B


• 1 C855B


• 16 SD40-
  (Modified, trail-only)


• 3 C30-
  (Modified, trail-only)

Highballing through Vancouver,
Wash., on July 30, 1976, an A-B-A
consist powers a UP intermodal
train. The GP30, GP9B, and
DD35A on this train were all hood
unit models that Union Pacific
purchased in both cab-equipped
and cabless versions new from
the builder. Garland McKee

16 SEPTEMBER 2019

LOCOMOTIVE

UP stripped the cabs on 19 EMD SD40-2s and GE C30-7s, effectively

making its own B units, in the early 1990s. Brian Schmidt collection