I would say cars because just go into a city and just look around thats all you will see
Bicycles give you more gas mileage.
Depends on where you're at. In Europe and North America - certainly. Some parts of Asia probably have more bicycles and scooters than cars though.
Bicycles are a lot more efficient than cars. On a bike 95-98% of the added energy is directly translated into forward motion, while a car would be lucky to reach 40%. While cars are definitely a faster way of transportation compared to bicycles, bicycles would probably be more efficient. Cars are very expensive and you must pay for gas. You also have to account for the distance and if its necessary to have a car for where you need to travel.
you can drive less and you can ride your bicycles and do more walking. Drive smart cars and make sure the cars are leaking less gas.
Cars and bicycles.
bicycles and cars
The more people use bicycles then the fewer drive cars. This will reduce fossil fuel consumption.
More bicycles
In Holland we use (besides cars) public transport (trains, buses, and trams/subway in the big cities), our bicycles (there are more bicycles than people in Holland) and we walk.
Netherlands
No
To make then easier to be spotted by cars.