Here are the answers matched with the sentences:
You must stop when the A is red. (A: Traffic light - matches statement about stopping when the light is red)
It's quicker if you take the F through the mountain. (F: Tunnel - an underground passage)
Always check the road before stepping off the B. (B: Sidewalk - a place where pedestrians walk next to the road)
You can cross the street at the G. (G: Crosswalk - end of the information)
Pay attention to the H so that you don’t get lost. (H: Signposts - they give information to drivers)
You have to cross the E to get over the river. (E: Bridge - it allows people or vehicles to cross over a river)
Cars are not allowed to drive in the C. (C: Bus lane - only public transport vehicles can travel along it)
Drivers should be careful of trains when going over a D. (D: Level crossing - a place where a train crosses a road)
So it would be:
- A
- F
- B
- G
- H
- E
- C
- D