Hi Danny,
probably the emissive mesh of your lightbars is just compounded to LOD0. To check this try increasing the distance that renders the LODs in your vehicles.meta like this:
<lodDistances content="float_array">
500.000000
500.000000
500.000000
500.000000
500.000000
500.000000
</lodDistances>
be carefull, this might be challenging for bad PCs.
If this fixes your problem, you need to modify the vehicle in zmodeler.
best regards
Sammy