The objective in counting vehicles at each stop is to produce information about

• the overall level of human activity along a route

• any changes in this level from year to year

A simple way to estimate human activity is to count the number of vehicles during a three-minute period at each stop.   Usually you can count vehicles during the same three minutes you count birds.   Any contraption moving on the ground with a motor counts as a vehicle!

If you extend the three minutes for counting birds to compensate for heavy traffic, do not make an extension for the traffic.   Instead just count vehicles during the first three minutes -- whether or not the traffic is heavy!

If things are happening fast (lots of birds, lots of traffic), then the birds come first!   Count the birds the best you can -- and estimate (guess) the number of vehicles the best you can.