Teen brains and driving: The one 'request' all parents should ask of P-platers

As the eldest of three sons, I was the first to get my driver's licence. After the initial shock that I actually passed my driving test the first time (I am a terrible driver - my father says I don't drive a car, I aim it!), Dad sat my brothers and I down and shared with us his one rule when it came to driving, i.e., he never wanted for one of us to be behind the wheel and the other two to be passengers in the car. His explanation was simple - young drivers aren't experienced and accidents happen, to have one of his sons in a car crash would be bad enough, to have all three in that vehicle would be devastating.

Over 4 decades later I cannot think of a time when the three of us have ever been in a car together with one of us driving! For some reason the discussion we had all  those years ago just stuck!

This rule certainly did not come about as a result of my Dad's extensive knowledge of research in the area (in fact, I doubt whether any really existed back then), it simply came out of his love for his kids and awareness that young drivers are more likely to make mistakes. In recent years we have seen so much research conducted in this area and when you look at what we know now my Dad was away ahead of his time!

When you look at the Australian statistics around young drivers, and particularly P-platers, it is no surprise that parents are concerned ...

• 45% of all young injury deaths are due to road traffic crashes
• almost half of all hospitalisations of young people are drivers, another quarter are passengers
• young drivers (17-25 years) represent one-quarter of road deaths, but are only 10-15% of the licensed driver population
• a 17-year-old with a P1 licence is 4 times more likely to be involved in a fatal crash than a driver over 26 years

Most importantly, studies have now identified passengers and number of passengers as key factors associated with increased fatal crash risk for young drivers, with one US study's (Chen et al, 2000) results bound to cause great concern for any parent of a P-plater. As shown in the infographic above, compared to driving with no passengers, a 16- or 17-year-old driver's risk of death per mile:

• increases 44% when carrying one passenger younger than 21
• doubles (increases 102%) when carrying two passengers younger than 21
• quadruples (rising 339%) when carrying three or more passengers younger than 21

Interestingly, having an older person in the car seems to have the reverse effect, decreasing the risk of death by 62 per cent when passengers aged 35 or older are present.

These findings mirror those tragic stories of groups of Australian teens being killed in car crashes involving P-platers. Too often these involve three or four young people being in the car when the accident happened. As a result of growing research, as well as in response to the deaths that have occurred, we have seen some countries, including Australia, impose restrictions on the number of peer passengers young drivers are permitted.

I can remember when NSW first introduced legislation limiting the number of passengers P-platers were allowed to have in their car. I fought it hard! In my dealings with young drivers, particularly around drink driving, I have always heavily promoted the concept of the 'designated driver' and believed then (and still do) that the vast majority of teens would never even consider driving home from a party after drinking. It is important to acknowledge that some studies have found that having passengers in a car can have positive effects on drivers, although these are reduced the younger they are. Passengers can help keep drivers alert, help them navigate, operate the radio or other communication devices such as mobile phones and even take over driving when necessary. Limiting the number of passengers P-platers were allowed to transport seemed incredibly unfair to me ... I then attended a conference in Geneva and heard about some research that changed everything ...

A Dutch study found that the older a driver gets their driving licence, the lower the initial risk (Vlakvled, 2004). You could have as many lessons as you wanted but the earlier you started driving, the more likely you were to have a crash. If you started driving after 21, with fewer lessons, your risk of a crash dropped and further reduced the older you got. There just seemed to be something about young drivers that put them more at risk. Experience certainly mattered (and that is why we are seeing many jurisdictions continue to increase the number of hours learner drivers must complete before getting their licence), with crash rates over time being lowest for those who got their licence at age 18 and highest for drivers licensed at ages 30–40 (i.e., if you got your licence early you were less likely to have a crash later in life), but why was there this initial 'high risk' time?

There is now growing evidence to suggest that this could be due to brain development. Recent research has found that between the ages of 18-19 and 21-22 there is a 10 per cent reduction in accident rates, even when driving experience is taken into account. Gender also appears to be a factor, with three times as many males being involved in crashes. When you look at this data and match it to what we know about adolescent brain development, it clearly matches up ...

We now know that the brain doesn't finish developing as early as we once thought, with females fully developed at around 21-22 years and males much later (at around 25-26 years at the earliest). When you look at the crash data, it's at that age when you start seeing rates of crashes and casualties/fatalities significantly decrease. Yes, they're becoming more experienced drivers but they're also getting a fully-developed brain.

We know that several parts of the brain are used when driving. These include:

• frontal lobe – dealing with judgement and decision making 
• parietal lobe – managing information from all the senses
• occipital lobe - the visual cortex, interpreting visual information the driver receives
• temporal lobe – dealing with sounds heard by the driver
• cerebellum and other areas outside the cortex – controls muscle movement and balance

We know that the brain develops in a back to front pattern, with the frontal lobe the last to 'complete'. With that in mind, one recent study attempted to find out the impact of this development, particularly the prefrontal cortex (PFC), had on driving (Foy et al, 2016). The results were not necessarily surprising but incredibly important. They found that younger drivers had reduced PFC activity compared to older drivers and concluded that "the reduced activation in younger drivers may be related to prefrontal maturation which could contribute to the increased crash risk seen in this population."

What I found particularly interesting and important when it comes to messages for parents of P-platers is that this 'increased crash risk' was not necessarily due to less impulse control but insufficient perception and attention leading to driver error – i.e., driving had not yet become an "automatic task". Most of us as adults can relate to driving on 'auto-pilot' at some time or another, i.e., that time when you're driving along and all of a sudden realize that you're in the next suburb and you can't quite remember those three sets of traffic lights you must have gone through. As experienced drivers with fully-developed brains, we are able to drive on 'auto-pilot' and still react to sudden or unexpected events ... young drivers are unable to do this ...

I think we tend to believe that the multiple deaths that occur on the roads with P-platers behind the wheel are simply the result of passengers urging the driver to take greater risks, or being distracted by talking, movement or some other activity. Certainly, research has shown that 6 out of 10 young driver crashes are due to distraction of some kind, but it is now becoming more evident that brain development may also be playing a role in these tragic events. It doesn't necessarily have to be a group of 'lads' in a car that leads to an accident, having any same-age peers (no matter how responsible they may be) increases the risk of a crash because a P-plater does not have a fully-developed brain and driving has not yet become 'automatic' ...

By the time your son or daughter starts driving they are well and truly becoming young adults. If they are living in your home, they should still abide by your rules, but when it comes to driving, there is very little you can do to control what they do behind the wheel of a car once they leave your driveway. I reckon my Dad got it right, at least to some degree - he was thinking of his family and ensuring that if something went wrong he didn't lose all of us, what we know now is a little more complex ... For parents of P-platers I would recommend that you try to get them to agree to just one simple request when they start driving and that is as follows:

"Whenever possible, never drive with anymore than one passenger whilst on your P-plates"

Now I realize that this could be a hard-ask but it's certainly worth a try. When you look at the figures (and you can try showing them but realistically they're at an age where they just don't think it will happen to them!), trying to push them in this direction is well worth the effort. The vast majority of P-platers wouldn't even consider drink driving (their parents are more likely to do that than they are!) but they think nothing of having a couple of friends in the car and the evidence is clear that this is a significant risk ...

References
Chen, L., Baker, S., Braver, E., & Li, G. (2000). Carrying passengers as a risk factor for crashes fatal to 16- and 17-year-old drivers. JAMA 283, 1578-1582.

Foy, H.J., Runham, P. & Chapman, P. (2016). Prefrontal cortex activation and young driver behaviour: A fNIRS study. PLoS ONE 11

Vlakveld, W.P. (2004). New policy proposals for novice drivers in the Netherlands. Behavioural Research in Road Safety: Fourteenth Seminar, 194–204.