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“Road Toll”: Bad language, lies, damn lies and statistics

This is a version of a diary article I wrote on 3 January 2009.

As I write this, the Christmas holiday period, characterized by a morbid attention to road traffic accidents, has just finished. It seems that Victoria took first place in the “road toll” statistics. Given the sums that CityLink charges, I could believe that—if you miss a sign on Batman Ave. in the south of Melbourne's Central Business District, you'll owe CityLink about $13, even more if you don't find out in time and they have to come and get you to pay. But “Road Toll” has nothing to do with toll roads: it's more bad language, the term that the traffic authorities in Victoria use to mean “road accident deaths”. This seems to be a uniquely Australian and New Zealand abuse of the term.

Road accidents are sad, and it's understandable that the authorities are trying to do something about them. But do their attempts make sense? Victoria already spends more police time than any other state in attacking the perceived causes of these accidents. It's clearly not working. What are they doing?

Executive summary

This is a long article. Here are the key points:

Holiday road toll: nothing special?

According to the reports, Victoria had 304 road deaths in 2008, or 0.83 per day. Over a 14 day period, that would be 12 deaths. In fact, over the “road toll period”, which I assume to be 14 days, 16 people died. Four died on the last day, so for the rest of the period, there were 12 deaths in 13 days, or 0.92 per day. Is this even statistically relevant?

Arrive or live?

The Victorian Government has created a new 10 year plan called Arrive Alive—certainly an idea with which everybody should agree. But sometimes I think they place more emphasis on “alive” than on “arrive”. The main methods that they advocate—if you can believe the summary on the home page—are limiting the activities of inexperienced drivers (only one passenger allowed) and restricting speeds (thus making it more difficult to arrive, and discouraging people from travelling). No mention of alcohol, no mention of safe driving practices such as adapting to the road conditions or keeping your distance from the car in front of you—a thing at which Victorian drivers are not good.

“Speeding: our number one killer”

On 11 December 2008 I drove from Briagolong to Dereel and saw a sign on the central verge of the Gippsland freeway. It read something like: “Speeding: our number one killer”. Unfortunately I wasn't able to get a photo. But what stupidity! I'll get back to that later on.

The government has found a way to blame all issues onto “speeding”, which I interpret as exceeding the legal speed limit—certainly that's what they mean when you get fined for “speeding”. Clearly just about any accident (apart from a few freak exceptions) is going to be made worse with increased speed. But speed is just one of the issues and almost never the cause. My aunt Ursula, a dentist, once said “in case of doubt doctors always put ‘heart failure’ as cause of death—every single person who dies experiences heart failure”. In the same way, every traffic accident involves speed, even if it's less than 1 km/h.

But if you believe official propaganda, you would think that speed is the most important cause. Much of it is misleading. At http://www.vicroads.vic.gov.au/Home/RoadSafety/SpeedingAndSafety/TheFacts.htm you can read:

Small speed reductions save lives

Research shows that the risk of injury in a crash doubles with a 5 km/h increase in travel speed. Travelling at 65 km/h in a 60 km/h zone, you are twice as likely to be involved in a crash. A car braking from 65 km/h will still be travelling at 32 km/h at the point where a vehicle braking from 60 km/h has stopped.

I have a number of issues with these two statements. Firstly, they're unrelated. The first refers to injury and death, as if they were interchangeable, and the second to speed. In this case, they're barely related, as I'll explain. For the first claim, which research shows it? Without substantiation, this statement is barely more useful than the claims that Wendy McLellan makes about the Dereel phone tower.

The second claim is the real issue. It's extremely misleading. It bases on the complicated relationship between speed and distance when braking. At the speeds mentioned, your speed only drops significantly towards the very end of the braking manoeuvre. It's important to understand that, but this document tries to make it into a life-saver. It isn't.

The time it takes to come to a stop depends on how heavily you brake, of course. With tyres (friction) the limit deceleration is the standard gravity of gravitational coefficient 9.81 m/s². A more attainable deceleration would be about 8 m/s². At the speeds mentioned, the bulk of the distance travelled is taken up by the reaction time.

Taking these values, and with the help of a little program, it's relatively easy to come to the following results:

Speed   Speed   React   React   Decel   Decel   Total   Total
(km/h)  (m/s)   Time    Dist    Time    Distance Time   Distance
 60.00   16.67    2.00   33.33    2.08   17.36    4.08   50.69
 65.00   18.06    2.00   36.11    2.26   20.38    4.26   56.49

So at 60 km/h it takes you a little over 50 metres to stop. At 65 km/h it takes you 5.8 metres (about 11%) more to stop. How fast is the vehicle going in the second case 6 metres before it stops? Again, the program can help. “Sample distance” is the distance at which you sample the speed; if I had been more interested, a graph might have done a better job.

Speed   Speed   React   React   Decel   Decel   Total   Total   Sample  Sample  Sample
(km/h)  (m/s)   Time    Dist    Time    Distance Time   Distance Dist   Speed   Speed
                                                                        (km/h)  (m/s)
 65.00   18.06    2.00   36.11    2.26   20.38    4.26   56.49   50.69   34.67    9.63

That's quite close to what they claim—in fact, they claim less than what my program calculates. So what's the issue? Look at the other values. In each case it will take a little over 4 seconds to stop. In that time you'll travel over 50 metres. The fact that your speed is still relatively high 6 metres before you stop pales into insignificance when you consider how far you travel before you stop.

Presumably you've learnt to drive, very probably at a driving school. And your driving instructor will have reminded you again and again that braking is not the way to avoid accidents. This discussion shows you one of the reasons. My personal horror scenario is driving down a residential road with oncoming traffic and cars parked on either side. Then a child runs out 5 metres in front of me. I can't swerve, because there's nowhere to go. Can I brake? Sure. What will the result be? I'll hit the child.

For reasons like this many residential roads have speed limits like 30 km/h, or (in Australia) 25 km/h. I've even seen 15 km/h. Will they help? Here's the program again:

Speed   Speed   React   React   Decel   Decel   Total   Total   Sample  Sample  Sample
(km/h)  (m/s)   Time    Dist    Time    Distance Time   Distance Dist   Speed   Speed
                                                                        (km/h)  (m/s)
 30.00    8.33    2.00   16.67    1.04    4.34    3.04   21.01    5.00   30.00    8.33
 25.00    6.94    2.00   13.89    0.87    3.01    2.87   16.90    5.00   25.00    6.94
 15.00    4.17    2.00    8.33    0.52    1.09    2.52    9.42    5.00   15.00    4.17
 10.00    2.78    2.00    5.56    0.35    0.48    2.35    6.04    5.00   10.00    2.78

Independent of the speed I'm travelling at, I'll hit the child before the reaction time expires. Braking doesn't work. Keeping people off the roads does, but it's still far more dangerous than “speeding”.

But this is all not the point: how often do you avoid an accident by coming to a complete stop? Almost never, and in those cases where you do, you're probably going very slowly. In VicRoads' example, it takes over 50 metres to stop from 60 km/h. Most surprises are much closer. As any driving instructor will say, braking is the last resort. Consider the situation at higher speeds: at 100 km/h (still allowed in many parts of Victoria, even in the residential area outside my house), your total braking distance is over 100 metres. And at 240 km/h (yes, that's legal in some countries, for example Germany) it's over 400 metres. So at any speed, you can't rely on stopping to prevent accidents.

Those reaction times

In the previous section, I've assumed an average reaction time of two seconds. This isn't my invention; it's what I learnt when doing a course with the Institute of Advanced Motorists years ago. As I showed, the results tally well with the official figures, so they must be based on similar assumptions. A quick look through Google gives some typical results:

Two seconds does sound like a very long time, doesn't it? If you're reasonably alert, you take about 0.5 seconds to react (start moving feet and hands), and probably another 0.5 seconds to actually hit the brakes. But most drivers aren't tensed up waiting for an accident most of the time.

But what does that mean in practice? Consider the example of the child above, and make the not unreasonable assumption that you're on edge because of the danger involved, and the not so reasonable assumption that you will thus really be able to react in one second and not two. The table becomes:

Speed   Speed   React   React   Decel   Decel   Total   Total   Sample  Sample  Sample
(km/h)  (m/s)   Time    Dist    Time    Distance Time   Distance Dist   Speed   Speed
                                                                        (km/h)  (m/s)
 30.00    8.33    1.00    8.33    1.04    4.34    2.04   12.67    5.00   30.00    8.33
 25.00    6.94    1.00    6.94    0.87    3.01    1.87    9.96    5.00   25.00    6.94
 15.00    4.17    1.00    4.17    0.52    1.09    1.52    5.25    5.00    7.22    2.01
 10.00    2.78    1.00    2.78    0.35    0.48    1.35    3.26    5.00    0.00    0.00

So at the recommended 25 km/h there would be no difference. You'd still not have started braking before hitting the child. At 15 km/h you'd still hit the child, but possibly not do much harm. Only at 10 km/h would you be able to stop.

“Speeding”: a waste of time?

VicRoads continue with the next claim:

Speeding saves little time

It's true! Speeding is a major contributor to Victorian road deaths and trauma, and yet brings about only minor reductions in travel time. On a 10 km journey, you would save 46 seconds by increasing your average speed from 60km/h to 65km/h, but you double your chances of being involved in a crash.

If you accept the previous claim, then this is a logical consequence. But is that the issue? In areas with a 60 km/h limit you're unlikely to be able to go much faster anyway. The real issue is on long distances between towns. Most Australian highways are very good, there's little traffic, and I find it possible to keep up an average only slightly below the speed limit. I can usually manage the 620 km from Dereel to Echunga in 7 hours. Of that, about 90%—let's say 550 km—is on open roads where I could equally well do 130 km/h, in some places over 160 km/h. At 100 km/h, this part takes 5½ hours. At 130 km/h it takes 4¼ hours—a saving of nearly a quarter.

And where's the proof?

All we've seen so far have been claims based on shaky theories. What really kills people? If you're drunk and you drive off the road, does the accident get blamed on speed or alcohol? What if your car is in poor condition and a wheel falls off?

The report in The Age gives some details about how people died, unfortunately not for all of them. But in no single report did anybody blame excessive speed as the cause of death. Collisions with oncoming cars or trees are surprisingly common. It's difficult to see how speed can be the main cause of this kind of accident.

The Australian Government maintains a Fatal Road Crash Database, but unfortunately it doesn't seem to contain any indication of the cause of the accident. Maybe they don't keep this information. But without doing so, you can't analyse the problems.

Other dangers on the road

There are many forms of dangerous driving, and I'm not going to go into them all here. Many are exacerbated by excessive speed. This has nothing to do with speed limits. Safe speeds depend on many factors, and they certainly don't come in steps of 10 km/h. For example, traffic conditions greatly influence the safe speed. If visibility is down to 50 metres, you can't safely drive beyond 10 km/h, even if the speed limit sign say 100 km/h. If the road is icy, you need extreme caution (on the Western Highway a sign recommends 40 km/h, which is far too high for these conditions). But what about your position on the road? If you're less than your reaction time behind the car in front of you, and he brakes suddenly, you'll probably hit him. Again the value “2 seconds” comes into play. But on those same freeways where you'll get fined for doing 107 km instead of 100, people continually drive with distances of less than a second from the car in front of them. The police are out there looking for traffic offenders—hundreds of people can confirm that—but they don't seem to worry about keeping your distance.

The Victorian problem

Drive anywhere in country Victoria and you'll be faced with a barrage of signs with buzzwords like “ONLY SLEEP CAUSES FATIGUE” and “OPEN YOUR EYES” and “TIRED? MICROSLEEP NOW”—or something like that. If “speeding” is the number one killer, it seems that going to sleep at the wheel is number two. But why? I haven't seen this identified as a serious problem elsewhere. And the interesting thing is, yes, I find myself getting drowsy when driving in Victoria too. The long, empty roads are hypnotic at the speeds we're allowed to drive. I've driven similar distances in other countries and never had this kind of issue. Until proof of the contrary, I assume that this is one more negative side of low speed limits.

Let's ignore what we can't measure

Another report mentions statistics for various kinds of traffic offence: “more than 900 drink-drivers were caught across the state”, but the same operation caught 8247 “speeding” motorists. There is no mention of anybody being booked for driving too closely to the vehicle in front of him. Clearly it's easier to catch “speeding” motorists.

And elsewhere?

Victoria may have some kind of record in obsession with speed, but it seems to be an anglocentric problem: the USA and the UK are not much better. In continental Europe, things are different. Despite significantly higher traffic densities, speed limits are considered secondary to other traffic behavioural issues. In Germany there is no general speed limit on the freeways. People regularly drive at speeds round 200 km/h, and the slowest cars drive at about 120 km/h. Some lanes on German freeways have minimum speed limits of 120 km/h. If the policy makers are right, the German freeways should be a graveyard.

In fact, the documentation shows that road deaths on German roads are somewhat lower than in Australia, The Australian Government produced a document comparing the road deaths in Australia with other OECD countries in 2006. The results:

      Australia       France       Germany       UK       Victoria
Deaths per 100,000 people       7.7       7.7       6.2       5.4       6.6
Deaths per 10,000 vehicles       1.1       1.3       0.9       1.0       0.9
Deaths per 100 million km       0.8       0.8       0.7       0.6       0.6

So despite the draconian speed limits, a higher percentage of the Victorian population dies on the roads than in Germany. That would be surprising if the speed limits were the same: the freeways in Germany are very congested, and it leads to bad behaviour on the roads. The other two values are more indicative of the differences between Germany and Australia: people here obviously have more cars, and they drive further.

It's worth considering the implications of these statistics. The Germans obviously have something going for them that the Victorians don't, and by emphasizing the impact of “speeding”, the authorities are de-emphasizing the real issues.

What others think

This doesn't stop people saying the opposite. A few years ago in The Age a reader discussion contained the claim:

It is a significant fact that other countries with higher speed limits have higher road tolls.

Certainly this discussion shows a number of people in favour of the speed limits. Brainwashing works again.

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