Do traffic lights cause congestion?

Several months ago I listened to a traffic engineer being ignored at a Toronto City Hall public hearing as he described his idea to replace stop signs with yield signs and traffic signals with roundabouts to reduce emissions (he was right).

I have often heard the argument that traffic lights cause congestion. Martin Cassini is an anti-traffic-light person (so am I in my usual well-tempered way), but his argument that traffic control is a primary cause of congestion, rather than just another exacerbator, is exaggerated.

There are lots of contributors to congestion. The congestion-blind fuel tax architecture which perverts the pricing model is arguably primary as is wealth. Traffic lights cause local clotting and may cause unnecessary emissions. I say MAY because traffic signals when properly set up (which is decidedly difficult and seldom the case), can also act as gating mechanisms to let downstream traffic clear before sending in another blob of traffic. In rural areas and smaller towns and off peak hours in urban fringes red lights should be set to flashing amber all directions and motorists who generally wish to remain alive, or at least not damage their automobile, will slow to navigate these simple obstacles efficiently and safely.