British things - Are they possible?

When a map of Canterbury to Herne Bay (British) comes out I would like to extend it to Ashford via Wye. There are some British things that I would like to include but I don't know whether they are possible:

• Flashing Speed signs - If the speed limit on a road is 40mph and you go past at 50mph they activate an LED '40MPH' sign with flashing lights around it. Can I make one of these that works?

• Human Operated Level Crossing gates - Seen at Wye, these gates span the whole road and are opened and shut by a man. They do not go up. Will AI traffic behave and not crash through them?

• Car Speed Bumps - Buses straddle them, but cars have to bump over them, can I make the AI cars bump over them?

• Two-way roads only wide enough for one vehicle - the main road through Wye has parking on both sides. The road is two-way but there is only space to fit one vehicle. Sometimes buses get stuck. Can I make the AI cars get out of the way?

EDIT: Another thing: How do I create Road Surface Markings? (Like the arrows, but I want a busstop rectangle instead.)

There are speed hump objects, but not the centrally located humps you talk about. As far as narrow roads are concerned, I've put parked cars on one side of a standard 7m road, and used the invis_street spline to carry traffic along the narrower section. I tried this out and had a quintessentially british moment when another bus came the other way cause we both had to creep past each other with inches to spare lol.