PAGE SUMMARY – motorcycles are small and easily hidden… the motorcycle can be concealed by the vehicle itself or by objects outside the car… the A pillars either side of the windscreen have steadily got thicker to provide better crash protection… a ‘framing effect’ means we avoid looking at the edges of the windscreen… when two vehicles are moving towards an intersection and due to arrive at the same time, the ‘bearing’ between the two vehicles stays constant… if one vehicle is hidden when the bearing remains constant, it will remain hidden… even though the rider can see the vehicle, the driver may not see the bike…

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As we’ve seen the commonest collision between a motorcycle and another vehicle happens when the motorcycle has right-of-way yet the other vehicle turns across the motorcycle’s path. In the last post, I began to look at the research that has been carried out into the ROWV and the consequent SMIDSY collision and described four possible failures:

• the driver doesn’t look
• the driver looks but cannot see the motorcycle
• the driver looks but fails to see the motorcycle
• the driver looks, sees the motorcycle but still makes an unsafe manoeuvre

The previous section examined the first idea – that the driver simply doesn’t look – and concluded that whilst lack of attention or distraction may contribute to some collisions involving a motorcycle and another vehicle, it’s far from clear how many. In fact, it’s far more likely that the driver did look appropriately, but failed to see the motorcycle.

So let’s move onto the second issue – although these collisions often happen when witnesses report that they saw the motorcycle, does that mean that the driver can see the bike from where he or she is sitting?

It’s been noted many times (eg Olson (1989)) that because motorcycles are smaller than other road users, the view of the motorcycle may simply be physically obscured. Here’s are two straightforward explanations. The approaching motorcycle is not in a position to be seen by the road user about to commit the ‘looked but failed to see’ error because:

• it’s hidden by other vehicles, pedestrians or roadside furniture
• it’s hidden by part of the vehicle itself – most frequently the A pillars (the supports either side of the windscreen) are known to create blind spots for the driver

How often does this happen? In a study from Victoria, Australia in 1992, Hentlass (reported by Paine et al (2005)) found that in 37% of the collisions where the other driver did not see the motorcycle, the driver’s view was obstructed.

For example, two common collisions where the bike isn’t where it’s capable of being seen involve:

• a car emerging from a side turning into the path of an overtaking (or filtering) motorcycle
• a car turning right into a side turning crosses the path of a PTW moving to the left of the main flow of traffic (this is a common crash involving cyclists too)

In either case, the driver is blindsided by the vehicle(s) between the car and the bike and simply cannot see the motorcycle. Although most riders are actually dual drivers (ie holding a car license too) most of us give to little thought to just how difficult it is to see an overtaking or filtering motorcycle from a car and rely far too heavily on the driver turning cautiously. Crundall et al (2008) noted that both riders and drivers seem unaware of the issue, stating that:

“drivers and motorcyclists can be made aware of this form of obscuration, with the hope that drivers subsequently resist making hasty decisions in the face of high-sided vehicles that could be obscuring other traffic…”

However, it doesn’t require a high-sided vehicle to blindside a driver. From the driving seat of an average car, the majority of the motorcycle and rider will be hidden by another car if it is in the line-of-sight. The driver may catch a glimpse of parts of the machine and rider through the other vehicle’s windows but the only object that the driver is likely to be able to see clearly is the rider’s crash helmet. If the partial view of the machine is not recognised as being a motorcycle, the driver is highly unlikely to respond appropriately.

It’s not just other vehicles that block lines-of-sight. Anything that sits between the driver and the rider is a potential problem – pedestrians, tree and telegraph poles, letter boxes and phone kiosks. Even following another motorcycle can hide the second bike, which is something to consider when riding with a partner or group, even when training! The list of ‘vision blockers’ is endless.

In many cases, witnesses will state that the motorcycle was “in plain view”. To them, perhaps but the construction of the modern car itself results in significant areas outside the vehicle being obscured. If a car is sat directly facing oncoming traffic (when the driver is looking out of the windscreen) or at right-angles to a major road (when the driver is looking at of the side windows), the driver is looking through the middle of a window. But that’s not always the case:

• if the vehicle is angled towards the traffic flow, then the A pillar (supporting the front of the roof at the sides of the windscreen) can obscure the view
• if the vehicle is angled away from the traffic flow, then the B pillar (supporting the doors) and / or the C pillar (supporting the rear of the roof) can obscure the view

The A pillars either side of the windscreen are the usual culprit but it’s important to be aware when the B and C pillars, as well as headrests on seats and the passengers sitting on them, can severely restrict the driver’s vision.

How much of a problem are the pillars? Crundall (2008) quotes a Transport Road Research Laboratory (TRRL) report from 1963 that found that a pillar that obscured 4 degrees of the driver’s vision would conceal the END profile of a car at 60 feet (18.3 metres), and demonstrated how this ‘zone of obscuration’ could sweep across the background hiding a pedestrian, cyclist or motorcyclist. That TRRL report – over four decades old – recommended that A pillars should be designed to be as thin as possible, and preferably less than 2 inches (approximately 5.1 cm) wide, including the window frame. Crundall (2008) notes that vehicle design has changed considerably since 1963 with the A pillars becoming thicker to increase vehicle occupant safety. The then-current EU regulations, which allowed 6 degrees of view obscuration from a car’s A pillar, were found to be able to hide a car in SIDE profile a distance of 50 metres.

Since 2008, the A pillars have become wider to accommodate air bags and / or to improve roof strength in the event of a roll over. I’ve just measured the A pillars on a late model Skoda and found at the front the A pillar to be no less than 12 cm wide. Using an online calculator, if the driver’s eyes are around 45 cm back from the driver’s side pillar (the seat is fairly far back on the runners), then a 12cm wide A pillar obscures a cone of vision that across extends 15 degrees of view on the driver’s side. And as we know, the head-on profile of a motorcycle is considerably narrower than the side profile of a car. A TRL report reconstructed ten crashes in which it was thought A Pillar obscuration could have been a factor. Three involved motorcycles, all at T intersections where a car was emerging to turn right so the motorcycle was approaching from the driver’s right. In one case the motorcycle was obscured for 4 seconds and in the other two for about 2 seconds.

To get some practical idea of how much of our view is obscured by the A pillar, here’s a simple practical demonstration. Hold your arm out and lift your hand up so the back of the hand faces you. Your hand is pretty close to the thickness of a typical A pillar and at arm’s length, it’s approximately the same distance from your eyes as seen from the driving seat. Now step outside and stop about ten metres from your bike, looking at it head-on. Hold up your hand, and cover up the bike. Walk towards your bike and see how close you can get before you can see the edge of the machine around your hand. Having a narrow frontal area, it won’t be until the motorcycle is frighteningly close. Now it should be obvious why motorcycles can be out of sight for as long as four seconds. It’s worth pointing out that the rear C pillar in a typical hatchback is around twice as thick and creates huge blind areas, and there is also some evidence that the large mirrors on modern lorries and coaches create large blind areas behind them.

Even if the machine is visible around a windscreen pillar, it appears that we avoid looking near to the edges of a framed scene. The pillars represent the frame so the tendency is for the driver to look out of the areas of the windscreen which are well away from the pillars. So not only are the pillars a physical blind spot, this ‘windscreen zoning’ phenomenon creates a psychological blind area that is even bigger. Windscreen zoning appears to be something known in aviation circles where it has been implicated in mid-air collisions but is virtually unknown in road safety. I’m speculating but my guess is that it happens because the frame is at a different focal length to the scene visible through the frame, and this creates discomfort.

Another problem is created by movement. Here’s a quote from a yachting website:

“If you are watching another vessel approach your vessel and its “relative bearing” is not changing, then your two boats are on a collision course.”

This ‘constant bearing’ problem is well-known in nautical and aviation circles, and it’s also well-known that if another boat or a plane are on a collision course and hidden by some part of the structure, then the other craft will remain hidden almost to the moment of collision. The same applies on the road. If the approaching vehicle is hidden behind the A pillar when the driver starts to look to scan the road to check whether it is safe to emerge, and the two vehicles stay on a constant bearing, then the vehicle will remain hidden until it is close enough to ‘expand’ around the pillar. Although it’s most likely to be a problem when the car is stationary and waiting, and the motorcycle is approaching on a near-collision course, the constant bearing issue can arise when both vehicles are moving towards an intersection and due to arrive at the same time – see the diagram below.

Of course, the rider can usually see the approaching car, and makes the mistaken assumption that the driver has the bike in view too. And when the driver doesn’t stop, the rider is taken completely by surprise. The constant bearing issue almost certainly accounts for a number of collisions at junctions and roundabouts. It’s remarkable that this problem is almost unknown in motorcycling circles, but there is a solution as both sailors and pilots know – the motorcyclist only has to change speed and / or direction to get the machine out from behind the obscuring pillar.

Why don’t drivers simply move their heads to check into the blind spot behind the pillar? There’s a suggestion that when driving, we can actually become ‘blind’ to the blind spot itself. Crundall considers that:

“…drivers may theoretically understand the potential for windscreen pillars to obscure the road, yet may fail to heed the advice when it is needed. This is because the situation does not necessarily provide clues to the problem. The windscreen pillar may act in a similar fashion to the retinal blind spot… where the optic nerve joins the eye. At this point there are no receptors and the eye can process no information. Everyone has two such areas in their visual field where there is no visual information, yet the visual system extrapolates from the surrounding visual scene and ‘fills in’ the gaps such that these areas are not noticeable.”

As a result, we don’t see a visual stimulus that falls on the blind spot. Crundall suggests:

“…drivers may be so used to the obscuration posed by windscreen pillars that they are no longer noticed. Instead the perceptual system may fill in this ‘external blind spot’ and make it difficult for drivers to remember the potential problems of obscuration and to take preventative action to avoid it.”

Or, to put into just a few words, “out of sight, out of mind”.

How common is the ‘looked but could not see’ collision?

Olson (1989) pointed out that after a collision between a motorcycle and another vehicle, if the circumstances were such that the motorcycle was out of sight at the moment the driver turned into the bike’s path, the driver of the other vehicle would say that he or she “looked but failed to see” rather than “looked but could not see”. Olson reworked data from two earlier studies (including Hurt et al. 1981) to conclude that in 48% of cases where there was a violation of the motorcyclist’s right of way the view of the offending driver was obscured. Olson states that no mention is made of this in either study.

On the other hand, a 2006 TRL study argues:

“…whilst ‘A’ pillar obscuration can occur, there is rarely only one factor that contributes to an accident and at this stage there is not enough evidence to suggest that changes to the current legislation regarding ‘A’ pillar design would be of benefit.”

Whatever the numbers, it’s essential for us to understand that we could be invisible to the driver for a significant period despite being able to see the car quite clearly ourselves. Once we appreciate that we are in a blind spot, then it should be obvious why conspicuity aids such as day riding lights and hi-vis clothing cannot help prevent the ‘looked but could not see’ error. What we need to look for are ‘lines of sight’ – covered on CBT as ‘see and BE SEEN’. Ask yourself:

• what might be blocking another other road user’s view of me?
• if I’m not where the other road user can see me, what might happen?
• can I place myself where that other road user can see me?

We don’t even need to be concealed all the way to the point of the collision. Remember, we don’t have constant 360 degree awareness of what’s around us, but have to look in several directions and in a number places one ‘snapshot’ at a time. What we think of as ‘situational awareness’ is actually a cut-and-paste operation, joining these snapshots together. The danger should be obvious – if the motorcycle happens to be in the wrong place at the wrong moment, we won’t be seen despite the driver looking. Once we reverse-engineer the conspicuity issue this way, it’s a lot easier to understand why so of the ‘looked but failed to see’ collisions aren’t “because the driver didn’t look properly” but because the driver “looked but COULDN’T see”.

It turns out that we’ve been aware of this problem for even longer than I thought. I came across this interesting page on the Safe Speed site, which shows some pages from a book dating from as early as 1963. The diagrams clearly show the problems. We may argue that the driver should have taken extra care to look around windscreen pillars and other obstructions but debating who caused the collision isn’t going to prevent it happening in the first place. It actually seems almost inconceivable that with so many crashes resulting from PTWs vanishing in blind spots that motorcyclists aren’t better-aware of the problem. We don’t live in a perfect world, and the possibility that a driver might simply not have seen us should always be at the forefront of our planning. As long as we remember that, we can significantly reduce our exposure to ‘looked but could not see’ collisions.

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Page last update:

Wednesday 1 May 2019 – minor edits for clarity

Saturday 23 December 2018 – added link to the 1963 book on driver vision from cars

References:

Andreas, (2012) “What an RAF pilot can teach us about being safe on the road” retrieved from http://www.londoncyclist.co.uk/raf-pilot-teach-cyclists/

Crundall, D,. Clarke, D., Ward, P., and Bartle C. (2008) “Car Drivers’ Skills and Attitudes to Motorcycle Safety: A Review”. School of Psychology, University of Nottingham

Olson, P. L. (1989), Motorcycle Conspicuity Revisited, Human Factors, 31(2), 141-146

Michael Paine, M., Paine, D., Haley, J., Cockfield, S. (2005) “Daytime Running Lights for Motorcycles” ID 05-0178 National Highway Traffic Safety Administration

“Investigation into ‘A’ pillar obscuration” – a study to quantify the problem using real world data”,
TRL Report No. PPR159, March 2006

Last updated:

Friday 21 December 2018 – minor edit for clarity
Friday 23 November 2018 – minor edit for clarity

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