DTT Speed and Stopping Distances 1 — Questions and Answers
Question 1: What is the default speed limit on a national road in Ireland when no other limit is posted?
- 80 km/h
- 100 km/h (Correct answer)
- 120 km/h
- 60 km/h
Correct answer: 100 km/h
The default speed limit on national roads (N roads) in Ireland is 100 km/h when no other limit is displayed.
Question 2: What is the default speed limit for cars in a built-up area in Ireland?
- 60 km/h
- 30 km/h
- 50 km/h (Correct answer)
- 40 km/h
Correct answer: 50 km/h
The default speed limit in a built-up area (urban area) in Ireland is 50 km/h unless road signs indicate otherwise.
Question 3: What is the national motorway speed limit for cars in Ireland?
- 100 km/h
- 130 km/h
- 110 km/h
- 120 km/h (Correct answer)
Correct answer: 120 km/h
The speed limit on motorways in Ireland is 120 km/h for cars and motorcycles.
Question 4: What is the total stopping distance made up of?
- Reaction distance and braking distance (Correct answer)
- Thinking distance and reaction distance
- Braking distance only
- Speed distance and halt distance
Correct answer: Reaction distance and braking distance
Total stopping distance is the sum of reaction distance (the distance travelled while the driver reacts) and braking distance (distance to stop once brakes are applied).
Question 5: How does doubling your speed affect your braking distance?
- It doubles
- It triples
- It quadruples (Correct answer)
- It stays the same
Correct answer: It quadruples
Braking distance increases with the square of speed, so doubling your speed quadruples your braking distance.
Question 6: At 100 km/h on a dry road, approximately how long is the total stopping distance for a car?
- 35 metres
- 55 metres
- 75 metres (Correct answer)
- 120 metres
Correct answer: 75 metres
At 100 km/h on a dry road, the total stopping distance is approximately 75 metres, combining reaction distance and braking distance.
Question 7: What effect does a wet road surface have on stopping distance compared to a dry road?
- No effect
- Reduces stopping distance by half
- At least doubles stopping distance (Correct answer)
- Increases stopping distance by 10%
Correct answer: At least doubles stopping distance
A wet road significantly reduces tyre grip, which at least doubles stopping distance compared to a dry road.
DTT Speed and Stopping Distances 1
What is the default speed limit on a national road in Ireland when no other limit is posted?