Traffic congestions and destination distance are the primary factors considered by people while choosing their mode of transport to work or other places. Cars and bicycles are being replaced with each other in different cities around the world depending upon the urgency and travel time to reach your destination.
In smaller cities or towns, where the workplace is at the outskirts of the city, people tend to prefer the cars over bicycles so that their commute time is less and they can reach their workplace on time. Moreover, riding bicycles for a long distance will make them tired and they will be left with little or no energy for their job work. In contrast, in metro cities people tend to ride bicycles to their offices as workplaces are considerably near and they save way more time by not getting stuck in the traffic if they drive to work by a car.
In my opinion, people switching to bicycles is a better change as it helps in reducing the pollution and traffic problems faced by metro cities. Riding a bicycle also contributes to good health, and reduces the expenses required for fuel consumption and maintaining your cars. However, for smaller cities, cars could be an exception as there are very few people using them, and it does not create a traffic congestion generally.
In conclusion, both cars and bicycles are essential and cannot be replaced with each other completely. So, mode of transport shall be selected as per the situation and location of your destination.