content: As to how often I check the sides, always and every time. Hell I keep an eye on side roads with stop signs when I don't have any sort of stop or caution sign. If a car is coming up to the intersection I always ask "are they stopping?" But this is a habit I have developed due to being a motorcyclist, you have to be aware as people cut you off all the time and regardless of right of way you will be the one getting treated by medical personal while they will just have an insurance claim.