Vehicles seem to be a current trend as the weapon of choice for mass killers. There has just been a terror attack in Barcelona where a van plowed into a crowd, killing a bunch of people. These vehicle ramming attacks seem to be occurring mostly in Europe although there was recently such an attack in the USA in Virginia. So the best thing I can think of to do is to simply be alert. These vehicle ramming attacks happen in cities or urban areas where there's lots of people so if you're in such an area be extra careful about keeping a lookout for a vehicle that might plow into people. Make sure you have enough room to dodge to the side in case a vehicle comes plowing in your direction and if possible try to run inside any nearby building.