Basic common sense will get you far in Tanzania. A political stable and relatively stress free safe country. By avoiding “stunts” on your own, isolated town areas and by listening to advise from your guide, will probably get you “home free”.
If you while on the road make sure your hand bag/luggage are placed on the floor, keep your camera and cell phone well inside the car, and close your window when stuck in traffic, you will be pretty safe.
If involved in a traffic accident, do like the driver is telling you, they are trained for these circumstances. If you by foot come close to an accident, stay away. Somebody else will have to deal with it, even if you are medical skilled. Panic and blame creates tension, and crowds like this attract the bad apples who might utilize a tragedy to empty some pockets.
There are no good reasons for walking around after dark, like almost everywhere in the world, so avoid it!