On motorways, lowering the speed limit at congested times leads to less congestion because cars don't have to be so erratic in their braking. Would the same policy work in an urban environment. i.e. would average journey times be reduced if the speed limit on main roads were reduced from 30 to something lower at various states of congestion?
/me starts a some background reading and checks out the potential of using our SCIAMA supercomputer.