Symptom

The measurement of Vehicle travel times results in a warning:
"Vehicle .. already passed start of travel time section .. at simulation time .."

Cause

You receive this warning when a vehicle passes the start of a travel time measurement twice.
This can happen if you have intersection-by-intersection static routing and/or U-turns. Then it is probable (given the random assignment of turning movements) that some vehicles are routed around the block and pass the same travel time measurement twice.

Resolution

There is no way to prevent this behavior other than defining longer static routes through the network or using Dynamic assignment.