A friend of my who visited Thailand once commented on the number of u-turns that exist in Bangkok. It seems that Thai civic engineers love using u-turns instead of allowing intersections. The logic behind this decision may be that instead of using red lights, which stop traffic, using u-turns allow traffic to flow continuously at all times. U-turns are used especially in conjunction with flyovers and bridges. This is especially true in the city where traffic conditions are especially bad and u-turns are used frequently. Large roads like Vibhavadi-Rangsit Road even has u-turns that go overhead in order to avoid stop traffic on that busy street.
The use of u-turns in Bangkok often restricts going straight on a road or making a right hand turn. For example, when I drive on the Ekkami-Ramintra Road and want to head towards my house, I have to make a left hand turn onto Kaset-Nawamin Road and then a u-turn at the next traffic light. Additionally, I cannot make a right hand turn into my soi because there is a cement center divider. I have pass my soi and make another u-turn in order to make a left hand turn at my soi. All these u-turns means that driving in Bangkok is often more difficult to maneuver than simply knowing where your destination is because you also have to figure out the complicated roads.
U-turns are places where drivers should be very carefully. Tonight on the drive home I saw an accident at a u-turn where the car making a u-turn obviously pulled in front of traffic and caused a collision. Cars making u-turns need to take care to stay to the rightmost lane as much as possible and watch for the cars heading towards them. Likewise, the cars which are going straight would be wise to change lanes as they approach u-turns. There are usually signs posted at 100 meter intervals starting at around 500 meters to let you know when the next u-turn is coming up. Of course, you should also slow down a bit and keep a watch out for those who are trying to make a u-turn.