有关u-turn

小胡同

最近查google map for directions, 经常会看到需要u-turn。印象之中好像在主路上不可以，不管是否有不可u-turn的牌子。平常也看到有人在红绿灯处做u-turn。
请问u-turn到底是不是合法的？
5 v, e; S: W( U+ c' Y' Z7 {! ~! T谢谢！

EightBelow

U-turns
• Do not make a U-turn unless you can do it safely and without interfering
with other traffic.
- F+ v; t2 _+ c" r0 k& A* i3 Z" E• Outside urban areas U-turns are not permitted on a curve or near the
crest of a hill where the driver of another vehicle cannot see your vehicle.
U-turns are not permitted in urban areas in the following situations:
$ I" C  \, a" ^; l" f• On a roadway between intersections.
  [( q; ]  e8 u; o2 G# S0 h  u/ }• Where a sign prohibits making a U-turn.
8 n7 r  b5 C7 L' {• At an intersection controlled by a traffic-control signal (traffic lights).
• At an alley intersection.

无语

有红绿灯的地方U-Turn是违规的。