Tyre Blowout at Speed on a Coastal Road
You are driving a four-wheel vehicle on a coastal road in Bermuda at 60 km/h. The speed limit is 50 km/h. The road has a soft shoulder on the left and a steep drop-off on the right. You have four passengers and luggage. Suddenly, you hear a loud bang and the vehicle pulls sharply to the left. You realise the left rear tyre has blown out. You are in the left lane of a two-lane road (one lane each direction). There is traffic behind you. You need to bring the vehicle to a safe stop.
1. Explain the correct sequence of actions to control the vehicle after a rear tyre blowout, and justify each action.
Read the worked answer
First, keep a firm grip on the steering wheel and do not panic. The vehicle will pull toward the side of the blown tyre, so you must counter-steer gently to keep the vehicle straight. Do not overcorrect, as that could cause a spin. Second, ease off the accelerator smoothly. Do not brake hard immediately, because that can transfer weight and cause loss of control, especially with a rear tyre failure. Third, allow the vehicle to slow down gradually by coasting. If you have a manual transmission, you can downshift to help slow down, but do not abruptly change gears. Fourth, once the vehicle has slowed significantly (below 30 km/h), gently apply the brakes to come to a stop. Choose a safe place to stop: avoid the soft shoulder on the left if possible, as it may cause the vehicle to sink or roll; instead, aim for a straight section with a wide shoulder or pull off to the right if there is space, but be aware of the drop-off. Actually, the soft shoulder is on the left, and the drop-off is on the right. The safest is to stop on the road if you can do so without blocking traffic, or pull onto the soft shoulder if it is firm enough. But given the drop-off, you should not pull right. You should slow down and stop on the left shoulder if it is safe, or continue to a wider spot. Fifth, turn on your hazard lights immediately to warn other drivers. Sixth, after stopping, place a warning triangle if you have one, and move passengers to a safe location behind a barrier if possible. Do not stand on the road. Finally, call for assistance.
2. Calculate the approximate distance you will travel before you can stop if you initially coast for 3 seconds before braking, and your deceleration during braking is 3 m/s². Assume you are travelling at 60 km/h when the blowout occurs. Show your work.
Read the worked answer
Initial speed = 60 km/h = 16.67 m/s. During the 3 seconds of coasting, you do not brake, so you travel at approximately constant speed (ignoring slight deceleration from rolling resistance). Distance coasted = 16.67 × 3 = 50.01 m. After 3 seconds, you apply brakes and decelerate at 3 m/s². The speed at the start of braking is still about 16.67 m/s. Braking distance = v² / (2a) = (16.67)² / (2×3) = 277.89 / 6 = 46.32 m. Total distance = 50.01 + 46.32 = 96.33 m. So you would travel about 96 metres before stopping. This highlights the importance of slowing down gradually and finding a safe spot, as 96 m is a long distance, and on a coastal road with drop-offs, you need to plan your stop carefully. Also, if you had braked hard immediately, you might have lost control, so the coasting phase is safer but increases stopping distance. Therefore, you should look ahead for a safe place to stop well in advance.