There is no such thing as perfect mathematically provable safety. However that's not to say there aren't ways you can improve your odds. Looking both ways before crossing the street, although not perfect, is a pretty good technique. Being wary of cars that aren't pointed directly at you but which are coming in your general direction is a good idea. To this end, doing things like walking on the left sidewalk (or the right sidewalk in the UK or Japan) can help you to be aware of cars that shouldn't be on a collision course with you, but might be anyway.

When at a crosswalk with a walk signal active and cars applying their brakes to stop, do you step out in front of those cars with the assumption that they will successfully stop, or do you wait for the cars to make a complete stop before stepping out in front of them? Assuming they'll successfully stop might be reasonable in some scenarios, but an unsafe assumption in others. It's the sort of context-dependent thing you need to be aware of regardless of what any laws written by people say. Be more wary of cars coming down hills than cars going up them. Be more wary of cars when the road is wet or icy. Be more wary of trucks than cars, particularly those that look to have heavy loads, and be more wary of cars whose brakes are squealing.

Respecting the laws of man is generally a good idea, but you must also always respect the laws of nature. The laws of man won't save you when you get on the wrong side of nature.