So, What if we all rode bikes? There are definitely some obvious advantages - we'd all be fitter, healthier, less stressed and have cleaner air, nicer countryside, and quieter towns. Sounds like a good idea doesn't it? However, there would be many disadvantages too.

Riding a bike in the summer is fine, but in the winter it isn't so nice. Would you still want to ride a bike in really bad weather? Bikes aren't much fun in strong winds, rain or snow.

Most people go to the supermarket to do their week's food shopping. Do you fancy riding back carrying 10 carrier bags full of potatoes, frozen fish fingers, bottles of cola, cheese, washing up liquid and lots more? No? We didn't think you would!

Can you imagine going on long journeys on a bicycle? You wouldn't want to cycle from Newcastle to London - it's about 450km and would take you about 4 days!

What about emergencies? When a crime has been committed, the police need to get there really quickly. An police car can travel at over 100km/h, but you can't cycle a bike much faster than 50km/h. Criminals would have plenty of time to run away.

Ambulances are also very important. You wouldn't be able to carry a sick person on a bike! They wouldn't be very comfortable, and you wouldn't be able to give them any treatment.

Bicycles wouldn't be any good as fire engines either. Fireman need lots of special equipment like hoses, ladders and oxygen tanks when they're fighting fires. How would you carry all of that on a bicycle?

A lot of the traffic on roads is made up of vans and lorries. They can carry things that are too big and heavy to fit in cars. If cars can't manage, how would bicycles cope? It would take hundreds of people on hundreds of bikes to carry the same amount as a lorry. It would be very dangerous too - can you imagine trying to carry a washing machine on your bike?!

So, it doesn't seem possible for everyone to ride a bicycle. That doesn't mean that we should all be driving cars around though. Have a look at Getting it right to see how we can travel more sensibly.