Traffic can be both pedestrian and foot based also regular car traffic will impact your deliveries.

I'm pretty sure people downvoting me have no clue about NYC and never you walked through Korea town during rush hour.

but it's only offered by bike or foot

I bike nearly 100% of my daily commute for the last 3 years. I am affected by traffic, not so much to the point that I am as slow as traffic, but traffic affects me to a discernable degree.

Bridge fail; increased load on bart.

Traffic jam == less aware driver which cause me to be more cautious on my route to work == slower... I bike 2 miles from home to Bart, then bike 1 mile from Bart to office... used to be greater distance...

So minimum 6 miles a day: ~260 work days a year = ~1560 Miles biked... *3+ years at a scaling factor of say, 80% is ~3700 miles commuted... my speed has always been based on external factors; traffic, Bart death, cal-train fullness/death, weather, etc...

It is a significant impact on timing... so to say that Rush is not subject to any of this is ignoring reality.

HOWEVER: I will admit that in dense urban environ, with bikes, bike always win..

So: I'd conclude based on own experience that traffic reduction, sans massive catastrophe to the biker, is ~10-20% BELOW WHAT AN UNFETTERED BIKER CAN DO (i.e. n cars at all)

A biker, assuming reasonable distance, should be significantly faster than a car, in dense urban.

So, I may have invalidated my GP post...