A charity that promotes walking, cycling and public transport says the new Active Travel Bill has the potential to be the "most effective public health initiative since the smoking ban."
Sustrans Cymru first suggested the new law in a petition to the Assembly six years ago.
It says that the networks of new routes created by the Bill will play a major role in persuading people out of their cars for shorter journeys but what is also needed are programs that will help people to take advantage of the routes.
The evidence shows that the easiest way for most people to get more exercise is to build it into their daily routine, but even though most everyday journeys are short, many of us still choose to take the car; in fact 20% of our car journeys are less than one mile.
The Active Travel Bill aims to get more people walking and cycling for short local trips as part of tackling the obesity epidemic and reducing congestion.
More top news
This week Carl talks to psychologist Amy McClelland about new research on the sleeping habits of babies.
For those who have mobility problems the idea of a walk in the Welsh mountains may seem unlikely. But this new scheme may change that.
Any rain will eventually clear this afternoon, bringing brighter weather behind it.