Final answer:
To cross or enter city traffic safely from a full stop, you need a gap that allows you to get up to speed. You should be able to walk at least 4 meters before a car reaches you.
Step-by-step explanation:
When crossing or entering city traffic from a full stop, you need a gap that allows you to get up to speed safely. The width of the average car is 2 meters, so in order to cross the road safely, you should be able to walk at least 2 meters further than the width of the car, or 4 meters in total, before the car reaches you. This ensures that you have enough time to cross without being in the path of the car.