Heavy Traffic

Monday again..Every Monday, there will be a very very heavy jam at toll Penang Bridge, i wonder why..If every vehicle maintain their speed, there would be no traffic jam..its can be jam few hours in the morning on every monday..From lorry to bus, from car to motorcycle, and when 5 lanes at toll decrease into 2 lanes on bridge, everyone try to be as fast as they can, since them, traffic jam occured..I have nice mood to work every monday, but when i arrive toll, my mood will turn into "down"..Where is the tolerance? i Wonder..