Mode share morning peak travel, inner ring suburbs, Melbourne (source data: Vista 2012-13)
Cycling is a player in urban travel. Exhibit shows mode share in morning peak travel, inner ring suburbs, Melbourne (source data: Vista 2012-13)

As I noted recently, data from the Victorian Integrated Study of Transport and Activity (VISTA) shows that bicycle’s share of all weekday trips in Melbourne’s inner ring suburbs is now 5.0%. That’s higher than either buses (1.4%) or trams (4.3%). In the morning peak period bicycle’s share in the inner ring is 7.4%, still higher than tram’s 6.2%.

That’s an extraordinary number given the ad hoc and generally low standard of infrastructure provided for cyclists. It suggests there’s still a lot of potential for cycling to win a larger share of all trips, especially journeys to work and education. Melbourne does better than Australia’s other big cities but there’s scope for them to do better too.

There’s consequently a compelling case for governments to increase dramatically the attention they give to cycling. A large part of what’s needed is better infrastructure. There’s also a need for better regulation. One area where there’s a high degree of dissatisfaction with current law is the dark tinting of car side and rear windows.

In Victoria, all windows other than the windscreen can be tinted to legally reduce the amount of light transmitted to 35%. Up to 1998, the minimum for front side windows was 70%, same as the current standard for the windscreen.

Very dark tinting provides a look many motorists want but it has a potentially dangerous – even lethal – downside for the growing number of cyclists on the road. They’re very vulnerable road users who rely on drivers being able to see them in all conditions including at dusk and at night.

Cyclists also need to see a driver’s face in order to estimate his or her intentions. They want to see where the driver’s looking and if he or she has seen them. Sometimes that requires looking through a side or rear window. A topical example is doorings; cyclists have to see whether there’s someone in the right hand side of a parked car because of the risk the person might suddenly open the car door.

The problem created by dark tinting is exacerbated at dusk and at night when many commuters are cycling home. It’s harder for drivers to see other road users – or to “connect” with cyclists and pedestrians – if the light transmittance through their vehicles side and rear windows is reduced to 35%.

The tinting industry argues that dark tinting is desirable to reduce UV light entering the car, lower the internal temperature, enhance privacy, and improve aesthetics.

The Institute of Transportation Engineers Australia and New Zealand Section (ITEANZ) counters:

Untinted window glass cuts out most harmful UV rays. The further reduction as a result of window tinting is minimal… Studies have shown temperature reductions of only around one degree in a moving vehicle as a result of having tinting and that the corresponding reduction on air conditioner load was almost insignificant.

Privacy and aesthetics are legitimate desires but this debate is about vehicles, not houses. The health of other road users is at issue. In any event, privacy seems a moot rationale given that windscreens must by law provide at least 70% light transmittance. In the United Kingdom and Europe, there’s generally a minimum 70% light transmittance required for the driver’s side window.

VicRoads’ web site expresses some of the concerns around dark window tinting:

Tinted windows can significantly reduce driver vision. This is likely to be more critical for the elderly and other people with even minor vision disabilities. Therefore, it is desirable that the light transmittance of windows on a motor vehicle is not reduced below the level as supplied by the vehicle manufacturer.

Notwithstanding these views, VicRoads isn’t convinced there’s a case for action to reduce dark tinting due to lack of evidence. ITEANZ cites a letter from the then Minister for Roads in 2013:

VicRoads is not aware of any crash statistics correlating the current level of allowed tinting with a significant increase in road safety risk. VicRoads will continue to monitor the situation and any related research that may indicate the need to review the current permitted visible light transmittance levels.

Another letter from the then Minister makes clear his reluctance to take action:

While I acknowledge that there is a range of research articles pointing to risk factors associated with reduced light transmittance, the absence of clear evidence of a general problem means the case for changing the existing in-service light transmittance levels is not strong.

But the absence of compelling evidence demonstrating a link between crashes and dark tinting isn’t necessarily because there’s no relationship; it’s because the basic information isn’t available. Crash statistics collected by police don’t record the degree of window tinting. Nor is there data on the extent to which dark tinting increases rider’s nervousness or discourages cycling.

I agree with the principle that it’s not good policy to make laws if we’re not confident they’ll work. In this case though, I think there are other arguments that matter.

As the Minister acknowledged, there is “a range of research articles pointing to risk factors associated with reduced light transmittance”. The theory suggests reduced visibility is dangerous even if the data to show it hasn’t been collected.

Another factor is that while we can’t be sure changing the law will reduce casualties, we can be reasonably confident it will increase cyclists’ sense of subjective safety, especially in relation to the risk of dooring.

Finding a solution will be difficult because it must involve winding back in some way the change introduced in 1998. There’s now an industry providing tinting and 35% light transmittance is generally accepted by motorists.

Ultimately, I think the key point is that the only real benefit from dark tinting (aesthetic) is entirely a private benefit. Cycling, on the other hand, has significant social benefits; moreover, the consequences for cyclists of reduced visibility are potentially catastrophic.