car mobility ?

That sentence doesn't fit together right.

I assume that the intent of the sentence is to predict that, due an increased number of cars on the road, there will be a decline in bicyclists.

From time to time there are criticisms of urban design that accuse it of "favoring cars over pedestrians" or something similar, and that by doing so it contributes both to traffic jams and to urban sprawl.

How about:
Cyclists will retreat gradually from street traffic due to the increased number of cars on the road.

thank you for your answer