Sure! Both speed and distance matters a lot for throughput. The advantage of pedestrian traffic is that designing for it reduces the distance people have to travel and that it combines very well in conjunction with public transport, unlike cars. Also, the speed of mixed traffic is inverse correlated to the number of vehicles, hence is a special case in this regard where throughput may decrease as the volume per lane increases. The overall point however is that a single train can substitute a staggering amount of private vehicles (and who doesn't love leaning back, listening to music and reading the news while commuting?).