Railing walls was first introduced in NFS5 (Porsche Unleashed, although at Outback in NFS2, you could bounce off that first wall). I noted during the first days of the demo of NFSU (the first one) that railing would also help lap time there (more like bouncing off the fencing in the garden section of Market Street).nice to see someone who got a start at ruining the online community..by f***ing up the normal racing tactics.
So railing the walls in NFSU2 isn't anything new. Look at any competitive lap with NFSU at Olympic or Stadium and you'll see wall bouncing / railing.
NFS5 was probably the worst on some tracks, like bouncing off the walls of the series of tunnels at Auvergne.
NFS High Stakes eliminated wall riding by making the walls (or any off track obstacle) stick like velcro to your car, slowing it down drastically. If EA wants to make a game where players don't ride the walls, I suggest they implement the wall physics of NFS High Stakes, it may not be realistic, but it definately forces the players to run clean laps. Better yet, line the walls with something that stops the cars, like tires, or large posts, street lamps would work here.
never knew walls have lower friction then the road... if so I suggest riding the walls instead of the road 
) gives a huge boost, for a relative long period! on the on straight roads u'r much fadter at top speed, and in the corners, u accelerate quicker.