Dr Neil Thorpe, Lecturer in Transport Studies in the School of Civil Engineering and Geosciences, discusses the difficulty of trying to ban smoking in cars.

"More than 500 health care professionals have signed an open letter to MPs urging their support for a ban on smoking in vehicles with children in. 

The ban forms part of the Children and Families Bill, which MPs will vote on in parliament today. If passed, it is likely that a requirement not to smoke in the car will fall to individuals because the police will find it extremely difficult to enforce.

A law might make people think about what damage their smoking could do to the health of children in the car but when deciding whether or not to break a law, they will also likely weigh up the perceived benefits of smoking against the risks of getting caught and the punishment they might face. If the perceived plusses outweigh the perceived negatives, then the ban will be ignored.

Enforcement challenges

But if people do choose to continue smoking, enforcing a law would be difficult. For much of the time a lit cigarette can be kept out of view, below the level of the dashboard. And trying to spot someone who is smoking and trying to evade the law makes it doubly difficult.

The police use fixed and mobile cameras to detect speeding as well as people using their mobile phone while driving. But unlike a mobile, which can generally be seen when it is held to a driver’s ear, cigarettes will be more difficult to spot. When taking a puff, drivers can be identified from front-facing cameras, but it is very unlikely (if not impossible) to get a clear enough image of a passenger in the rear of a vehicle with enough clarity to determine their age. So even if you capture an image of someone smoking, it will be difficult to prove beyond all reasonable doubt that there was a child in the rear.

Problems of proof

E-cigarettes add new problems to enforcing this ban. How do you prove from a camera image that the driver was in fact smoking a cigarette rather than an e-cigarette? Police run the risk of incorrectly stopping drivers.

Then there’s the issue of proving the age of passengers. Vehicles could be carrying someone under 18 or they could be a small adult. In some cases this might not be obvious and it is unlikely that the passenger would be carrying any form of photographic ID. And drivers can easily discard cigarettes (either in an ash tray or out of the window) if they feel they may have been spotted.

Cigarette smell in a vehicle, a full ash tray or even cigarette smell on the breath doesn’t automatically indicate that someone was smoking; tobacco odours linger and ash trays may take days to be emptied – it would be the police officer’s word against the driver’s that they were smoking a real cigarette. A driver could simply turn around and say “no, it was an e-cigarette” and produce one from their pocket. Drivers can be very clever at circumventing rules on the road.

Self-enforcement is the only way

The best way of enforcing a no smoking ban would be through self-enforcement – educating drivers about the health risks to the point where the perceived negatives outweigh the perceived benefits of lighting up.

The huge amount of support that this ban is receiving from health professionals may be what’s effective in getting it passed – as well as enforced by smokers with children. While risks of being caught and punished by the authorities are unlikely to be sufficient to deter drivers from smoking, a growing awareness that smoking in cars is bad for passengers may be what persuades people not to smoke rather than the law itself."

Published in The Conversation

published on: 10 February 2014