This isn't what you want, your question is based on a bad premise; that the cars would still travel the same speed. If 98% of the traffic were bikes, then the speed limits would need be lowered to bike appropriate speeds(15-25). No other accomodations would be needed then.
If fact speed limits should be lowered now, even with 98% of the traffic being cars. 43,000 deaths a year are too many.