Maybe you define the vehicle and especially the vType twice?
An example from Sumo at a glance:
<routes>
<vType id="type1" accel="0.8" decel="4.5" sigma="0.5" length="5" maxSpeed="70"/>
<route id="route0" color="1,1,0" edges="beg middle end rend"/>
<vehicle id="0" type="type1" route="route0" depart="0" color="1,0,0"/>
<vehicle id="1" type="type1" route="route0" depart="0" color="0,1,0"/>
</routes>
How do you define your vehicles?