Do infantry riding vehicles get a terrain modifier to defense normally or just whatever terrain modifier the vehicle they are riding on gets?
Example: a squad of 3 INF riding a GEV-PC in the open has normal defense. They are driven along a road into a forest. Do they get the 2x Def bonus for being in forest or no multiplier because as riders they aren't as agile? Similar with towns, 3x or only 2x (that the GEV-PC gets) because riding?
I've always assumed they DO get their terrain modifier if they are riding ON the vehicles (figuring they still have options like hiding behind hard points on the vehicle or diving off at the last second into a ditch if the vehicle is about to get killed). I also don't see anything that says they don't in rules.
Not seeing anything about them losing the def multiplier if they are riding IN vehicles either though. And I'm not sure that makes sense. Why would they be 3x harder to kill being in an exploding truck in the city vs in the open? They aren't really 'in' the city. They're stuck in a truck.
REF 5.11.2 Combat involving infantry riding vehicles.
The vehicle and infantry may both fire normally. After all, the speeding vehicle is a stable firing platform, compared to what these infantry are used to.
If the vehicle + infantry combination is fired on, the attacker makes one die roll for each attack on the combination, but calculates the odds separately for the vehicle and all the infantry and applies the results separately. Example: A Howitzer fires on a Superheavy Tank carrying two squads of infantry. The die roll is a 3. The attack is a 3-to-1 on the two infantry (so a 3 eliminates both), but only a 1-to-1 on the Superheavy (so a 3 has no effect). This procedure is followed in both normal combat and overruns. Note that a tank will often survive a hit that kills it's riders, but even if the vehicle is a truck, the battlesuited riders may survive the hit that kills the vehicle.