Abusing "first come, first served"?

We have two delivery drivers and two trucks where I work. One truck is smaller and easier to get in and out of traffic, the other truck has a larger capacity for deliveries but is very slow and has no acceleration for highway driving, but is also easier to get into and out of parking lots for deliveries.

The drivers have been told that use of the trucks is "first come, first served," basically.

On a day when the smaller truck would accommodate enough for either driver to make their deliveries, this is the scenario:

Driver 1 has a route that is in the same town where we are located. Since he would be doing a lot of driving in town and parking at businesses, the smaller truck makes his job easier as it is easier to maneuver, but the larger truck won't add as much extra time as his driving is somewhat limited on the route. Almost none of his driving will be in an area where speed limits exceed the top speed of the larger truck.

Driver 2 has a route that carries him much further from the office, with a lot of highway driving. Using the larger truck will literally add three hours onto the route for him, because of the issues with lack of acceleration and the fact that top speed of the truck is approximately 15 MPH under the highway speed limit.

Given this scenario, the first driver arrived at work this morning first in order to get the smaller truck which is the more convenient vehicle for either to use; however, he did not actually begin his deliveries until at least an hour and a half after the second driver had left to start his route.

Both drivers are paid on commission and no hourly wages for their delivery days, so the first driver is not taking advantage of payroll by taking possession of the smaller truck earlier on.

Is this abuse of "first come, first served," since the first driver actually arrived much before the time he intended to do the work, and the second driver arrived at the time he intended to work?

There are other factors in the equation which might lead me to have a biased opinion on the scenario, so I have tried to put in only the pertinent facts on this particular situation. What are your opinions?