An early morning downpour on Last Friday (Aug 20) caused several roads here to be flooded.

These summaries below are referenced to the answers of Christopher Tan, The Straits Times’ transport and motoring correspondent on some questions about driving through flood waters.

How safe is it to drive on a flooded road?

If you must drive on a flooded road, consider the:

  • depth of the water
  • the height of the vehicle you are driving

These two factors determine how likely water will get into the car.

What are the other risks of driving in a flood?

If you continue to drive when the kerbs are submerged or if you are in an unfamiliar location, you may not know where the road boundaries are. You could mount a kerb and get stuck, or worse, end up in a flooded drain.

When a vehicle’s wheels are submerged, the brakes may not operate optimally.

The risk of water entering the air intake will cause considerable damage to the engine. It will also stall.

If water enters the exhaust system, it might damage the catalyctic converter, which is costly to replace.

What if I am driving an electric car?

Electric vehicles (EVs) can tolerate higher water levels without an air intake or an exhaust. But the risk of water entering the vehicle and damaging the cabin and sensitive electronic components is still present.

The higher the water level, and the longer a vehicle remains on a submerged road, the higher the risk.

If the water level is high enough, it might even come into contact with a vehicle’s electronic control units (ECUs or computers which control various functions).

Again, this will cause considerable damage, and could cause the vehicle to stall.

Both EVs and combustion-engine cars have ECUs.

If I decide to drive on, are there things I should do differently?

When driving on a submerged road, proceed with a gentle and steady throttle. In other words, keep a slow and steady pace.

Do not lift your foot off or apply the brakes midway. This is to minimize turbulence and backflow, which might cause water intake.

You might want to follow a bigger, taller vehicle – like a bus or a truck – just to be sure you are on the right track.

If you are in a manual transmission car, stay in the second gear. If you in an automatic with an option to engage a lower gear, do likewise.

Go slowly, since braking and handling will be compromised on a flooded road.

After you have cleared the flooded area, apply the brakes gently for a minute or two to rid them of moisture.


What should I do if my car stalls in a flood?

If this happens, it is likely that water has entered the engine air intake. Do not restart the car, otherwise this might cause further damage.

If the vehicle’s main ECU is damaged, you will also not be able to restart it.

Switch on the hazard lights, and phone for help.

It is safe to leave your stalled vehicle and get to higher ground despite of getting wet.

When the water could continue to rise, it is hard to open the door once the vehicle is half-submerged.

References / Citation

Tan, C. (2021, August 20). Askst: Is it safe to drive through a flood? The Straits Times. https://www.straitstimes.com/singapore/transport/askst-is-it-safe-to-drive-through-a-flood.

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