Anna Soper's recent article on cycling in Toronto highlighted two key points in creating a safe environment for cyclists: decent infrastructure to keep cyclists separate from other traffic, and proper enforcement of traffic laws when cyclists and other road users have to mix. Compared with some other countries, the UK has relatively limited cycle infrastructure, and dedicated cycle lanes are comparatively rare.

We do though seem to have an increasing number of advanced stop zones (ASZs) at traffic lights – the painted-on boxes for cyclists at the front of the queue. ASZs have the potential to contribute to a safer environment by giving cyclists a visible position and a head-start on queuing traffic. But for ASZs to contribute to cycle safety, they have to function as they were intended.

An ASZ is made up of two stop lines – the first at the entry to the box, and the second further forward by the lights. When the lights are red, approaching motorists are required to stop at the first line (and are not allowed to enter the box). Cyclists may enter the box when the lights are red, but strictly speaking must do so from the "feeder" cycle lane which should accompany every ASZ. As the feeder lane is normally on the left, cyclists abiding by this rule will often have to undertake stationary traffic, a move which is discouraged.

Breaking the rules on ASZs is an offence, and you can be given a fixed penalty. For cyclists the maximum fixed penalty is £30, whereas a motorist can be fined £60 and given three points on their licence. Alternatively both cyclists and motorists can be prosecuted, in which case the penalties can be significantly more severe, especially if someone is injured.

Although it's an offence for a motorist to enter the ASZ at a red light, if they were already in the box when the light went red, it's not an offence to stop there – in fact the law requires them to do so. This makes enforcement more difficult, as the police actually have to see the car enter the box in order to know whether an offence has been committed.

I asked a number of police forces for statistics showing how many fixed penalty notices they issue to motorists for unlawfully entering ASZs. Legally this is the same offence as jumping a red light where there is no ASZ, so many forces don't keep separate statistics for ASZ infringements. For example, the Metropolitan police says that it has "no current operational requirement" for the separate information.

One force which does hold separate statistics for ASZs is the City of London police. A spokesperson told me that in the past three years City Police issued 12 fixed penalties to motorists for entering ASZs unlawfully. Yet in the same period it handed out just over 6,000 fixed penalties to cyclists for jumping red lights.

Why is there such a difference in the numbers? Inspector Dave Aspinall, of the City police's roads policing unit, said:

"City of London police officers take a targeted approach to enforcement within the Square Mile that tackles poor road use and makes the roads safer for everyone. It is an approach based on analysis of the collisions we see here in the City, [...] and any road user seen committing a traffic offence is dealt with appropriately and proportionately."

The Met uses the same argument – that it is acting as it sees fit to improve road safety. The Met does not separately record the numbers of motorists infringing ASZs, but does record the number of fixed penalties it hands out each year for red light offences as a whole. Since 2008 it has issued about 3,000 fixed penalties annually at the roadside to motorists for these offences. In the same period the number of fixed penalties for cyclists for red light offences has gone up from around 1,000 in 2008, to 1,700 in 2009, to over 3,000 in 2010. So the figures for cyclists and motorists are now roughly equal. The Met says that this is "a result of police attempting to make cycling safer in London".

Is this really making cycling safer at traffic lights? Clamping down on jumping red lights might prevent some collisions, but it doesn't help cyclists who stop at red , which is what ASZs are designed to do.

A study conducted for Transport for London in 2005 found that at traffic lights without an ASZ, 54% of the cyclists who stopped for the red light did so beyond the stop line and in the pedestrian crossing (which can be a separate offence). Where there was an ASZ, the study found that 40% of cyclists still stopped beyond the ASZ and in the crossing. The study didn't determine whether the cyclists were doing so because the ASZ was taken up by cars, but it suggests that (at least in 2005) cyclists didn't feel safe in ASZs. As Anna Soper said in her article about Toronto (attracting criticism from many commenters), some infringements of the traffic laws by cyclists must be due to the lack of enforcement of the rules designed to protect them.

What can be done to improve the enforcement of ASZs? Firstly, effective monitoring of enforcement activity might actually lead to more enforcement action being taken. So all police forces should be encouraged to record separate statistics on ASZ infringements.

More radically, ASZs could be enforced by using cameras to detect infringements. The Met has confirmed that camera technology of the kind already deployed in London for red light-jumping could be used to catch motorists entering the box on red.

But the placing of red light cameras is subject to guidance from the Department for Transport, which suggests that the cameras should only be placed at junctions where there have been collisions leading to deaths or serious injuries. And since 2007, local authorities no longer keep revenues from safety cameras, meaning the cameras are not self-funding. So the use of cameras to detect ASZ infringements would require action from the government: a change to the DfT's guidance, and more funding.

What do you think? How can cyclist safety at red lights be improved?

• Jorren Knibbe is a barrister and writes about cycling law at UK Cycle Rules. This article is for information only and is not intended as legal advice.