Most of the main roads in Doha are two or three lane dual carriageways. Traffic travels fast.
Whilst vehicles seem to obey the red light at major intersections, pedestrian crossings appear guided by different rules. Cars will carry on through the red light. Motorcycles have been known to weave around the traffic and carry on through the red light. An English expat was killed by a motorcycle in these circumstances last year.
The safest method of crossing is to ignore the green man and wait until all cars in all lanes have actually stopped, and possibly a row behind if there are large vehicles still moving. Once everything has stopped it is safe to cross.