Originally Posted by SylvainG

Not true. Take for example a 30 seconds red light and going 35 km/h. To gradually (and linearly to simplify the maths) slow down to 5 km/h at the turn of the green light, then 5 seconds to go back to your 35 km/h from the 5 km/h, your average speed would be 20 km/h. If on the other hand you stay at 35 km/h until the last 5 seconds then stop (moving speed also stops counting) then go from 0 km/h to 35 km/h in 7 seconds, your average moving speed would be 29,3 km/h.