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Posted by on Nov 21, 2009 in Safety | 19 comments

Combinations Cause Crashes — Situational Awareness

As I swerved to miss the pedestrian — who had stopped, started, turned, and then walked backwards at the intersection all without seeing me approach — I had all my attention on making sure I did not startle (or hit!) the person right in front of me.

What I forgot was to watch for turning cars.  And there was one.  Since both of us (the car driver and me) were watching the wayward pedestrian, we both didn’t see each other entering the intersection.  Thankfully, we both were operating at such slow speeds that each was able to stop way before any crash would have occurred.

But this event triggered a thought in my head:  I didn’t see the car because all my attention was on the pedestrian.  I wonder how many crashes are due to situations where there are more than two events happening at the same time?

Crash Statistics

crash pie

Mighk has presented us with some wonderful crash statistics that breaks down bicycle crashes into nice categories.  But the categories are one-event situations (ie riding without lights, riding on the wrong side of the road).  I’m guessing (I hope Mighk will chime in on this) that it’s difficult to present this data when multiple events are the reason for a crash.  But, it shouldn’t be to hard for us to imagine some combination events — for example, riding on the wrong side of the road at night without lights.  And I bet if we could dig deeper, we’d uncover many other crashes where if there had not been a certain combination of events, it’s possible there would not have been a crash.

Situational Awareness

I recall Keri talking about her training as an aircraft pilot …. that as part of their training, they look at airplane crashes and break down the events or actions that led up to the crash.  Typically, it was not one single event or action that led to the crash, but rather a combination of situations and mis-steps — a chain of events.  If any link of the chain could be removed, in most cases, there probably would not have been a crash.

Their training was to drill into their minds that even while dealing with an immediate event, it was critical not to lose what aviation trainers call “situational awareness” — awareness of everything else still going on around them.  If the focus is entirely on the situation (crisis) at hand, you might miss out on a new (important) development, or you might not fully realize how your actions dealing with this one situation might place you into another.

How to use

This seems like a good lesson for all of us who cycle to keep in mind.  Many of us are experienced enough that we can recognize developing situations and take appropriate actions to avoid an incident.  However, if our focus is strictly on the one situation in front of us, we might be missing out on something else developing around us.

One way this can happen is when something out-of-the-ordinary takes you out of your normal cycling mental state.  That’s what happened to me when the pedestrian started acting funny.  I was mesmerized by the person’s “dance” on the sidewalk as I was approaching them.  What I needed to do was while keeping an eye on the pedestrian to continue to scan around me and prepare for the upcoming intersection.

One technique I know about (used by some motorcyclists) is to talk out loud (but quietly) to yourself about what is happening around you.  Like this: “… ok, coming up to intersection, light is green for me but is a bit stale. Car behind me but I will clear intersection before they arrive … car on right side is stopped but has his turn signal on; make sure he doesn’t pull out in front of me … going through light, all ok, car on right sees me, ahead all is OK except for that car parked on the side of the road, watch out can’t see through his windshield to see if he is in there or not, might open door or pull out … car that was behind me turned off … ok, all clear until I get to the next light …”

I know that this seems over-burdensome to talk out loud, but many of you do this sub-consciously anyway.  It’s a drill to try, and see if it makes you more situationally aware.

Perhaps some of you have other techniques you use, I’d love to hear what they are.

Anyway, as has been pointed out numerous time here, riding a bike is safe.  Safer than almost any other form of transportation.  But accidents (crashes) can happen, and it’s always good to know why.  As we get more experienced in our riding, we learn to eliminate the “one issue” causes of a crash.  But remember that a crash can be a sum or combination of several issues … and thus it helps if we can remain situationally aware even while dealing with what’s right in front of us.


  1. Andrew – What an excellent observation. I am an experienced, competent cyclist. The very few “close calls” I’ve experienced over the last few years have been precisely because of one thing happening simultaneously with another. I am sure it is often true for motorists too, but as you say, experienced cyclists are most often ready for threat #1, where I don’t think you can necessarily say that of most drivers.

  2. For “general audiences” I try to keep the charts simple, but yes, of course there are ways to communicate more than one factor at a time. In my Alternative Transportation course I have a pie chart with crashes by “approach:” crossing movements, turning movements, overtaking, head on. And since I’ve had many people tell me, after learning that overtaking crashes are relatively rare, that “those are the crashes that are going to kill you,” I filter out the night-time crashes (which usually involve ninja cyclists), and show what percent of each approach type involve incapacitating or fatal injuries.

    I’ve never analyzed bike crashes for such multiple threat circumstances; perhaps because they tend to fall in the “Weird/Other” category. The vast majority of bike crashes are fairly straightforward one car/one bike affairs.

  3. BTW, daytime overtaking crashes in our data resulted in 8% incapacitating (none were fatal during the study period). By comparison, turning movement crashes had 22% incapacitating or fatal, and crossing movements 12%.

    Note that these are predominantly urban/suburban crashes. If we looked at rural crashes the overtaking injuries would certainly be more serious.

  4. Because human beings are poor multi-taskers, it is vitally important that motor vehicle speeds be kept low to enable situations to be dealt with safely. I note that many cities are moving to 30 km/hr (18 MPH) maximum speeds throughout their urban areas, automatically enforced with photo radar.

    This seems to be a good idea for creating safe roads.

  5. While I’m all for what Kevin suggests in principle — especially in town centers — let’s be realistic. Our arterial and collector roads are designed for 40 to 50 mph. The motoring public — which is at least 80 percent of voters — will simply not stand for 18 mph limits (or even 25 mph) on those roads. Any traffic engineer who does it would be fired, and any elected official who supported it would be voted out of office.

    That’s why we’re focusing here on learning to use the system as it is.

  6. The idea of talking to oneself with a checklist of sorts is a great idea. I’ve flown with a couple of pilots who do that and my assessment of the flight has always been positive. Paper (or electronic) checklists are the norm in aircraft, so a verbal one on a bicycle is not far-fetched.

    I’d suggest that people normally perform such things without realizing it, but pointing it out in this manner makes it all the more effective, in my opinion.

    I have a few switches to toggle in my velomobile prior to starting off and while I don’t have a paper checklist, I do have one in my alleged mind. Unfortunately, it’s failed me on occasion and I neglect to turn on the rodney-cams or the taillight during a daylight drive, but these are not system-critical.

    I’m going to use Mighk’s reference to “approach” and develop a mental checklist for intersections, crosswalks, sidewalks, driveways, etc. Such a checklist would be a simple as “look everywhere!” and assessment would follow naturally.

    Friday’s ride brought me to an intersection at 30 mph, just turning yellow on the traffic light. Since oncoming traffic is supposed to stop on red before turning right, I had already assessed that area before rolling through on yellow. Okay, ripping through on yellow. Oncoming traffic driver turning red decided not to stop and occupied my lane at about the same time I wanted to be there. I had anticipated it, as I try to do, and had an open lane to my left for an escape route. Had there been another vehicle there, my brakes were already covered.

    A pedestrian in the crosswalk would have complicated things and I might have given priority to the pedestrian and overlooked the driver turning right on red without stopping.

    Andrew, you sure make good posts, clear, succinct and excellent image use in context.

  7. Excellent topic and post, Andrew!

    In addition to chain-of-events, the pedestrian story is analogous to another aircraft crash cause: fixating. I think the mental checklist works well to keep you scanning.

    Along the lines of chain-of-events, the first link is often poor lane position because it exposes you to overtaking problems (right-hook), decreases visibility to others, your sight lines, thus increasing your scanning workload. If you approach an intersection in the left tire track (vs the right side of the lane or a bike lane), you eliminate or reduce the majority of potential conflicts, thus reducing your scanning workload.

    I feel an animation coming on :-)

  8. Mighk wrote:
    “Our arterial and collector roads are designed for 40 to 50 mph…”

    Kevin’s comment:
    That’s incredible. 50 MPH = 81 km/hr. Which is illegal in Ontario in urban areas for very good reasons of public safety. With the only exception of motor-vehicle-only expressways (like the Queen Elizabeth Way) that are fenced in to exclude pedestrians and cyclists.

    Even in rural areas, highway speeds are limited to 80 km/hr. Generally, urban speeds are limited to 50 km/hr, with a moderately extensive 30 km/hr zone in Toronto. There are some limited 60 km/hr streets in non-residential areas.

    To have an 81 km/hr street in an urban area appears to me to be a situation in which politics overruled traffic engineering and safety engineering.

  9. In BC, quite a few highways have 90km/hr speed limits. There are many cars going significantly faster than that. At least the 85th percentile has a basis other than “I think that’s too fast” by do-good politicians. Removing factors that encourage people to drive faster achieve a better effective speed drop. People drive fast in Florida because they feel safe doing so. THAT is the speed problem there, not the posted limits.

    Part of cycling defensively is to anticipate and reduce the probability of multiple simultaneous occurrences. ESPECIALLY those that one has not trained to deal with. In an emergency, the need to THINK can be fatal…

  10. We have an ugly convergence of factors that have led to so many high-speed roads.

    * The aformentioned 85th percentile rule.
    * A law that makes driving less than 5 mph over the posted speed un-citable
    * Flat terrain, resulting is very straight roads
    * Suburban land use setting buildings way back from the street

    Step One: build a straight, flat road
    Step Two: set the posted speed at the 85th percentile level
    Step Three: put buildings far away from street
    Step Four: only enforce speed violations of 10 mph or more
    Result: average speeds are at least 5 mph higher than posted
    Step Five: when widening road, do speed study; find that 85th percentile is now 5 mph higher than original
    Step Six: design road for higher speed
    Step Seven: do speed study of wider roadway; set new 85th percentile speed which is based on the faster design and faster traffic; add another 5 mph

    • Step Eight: Claim the road is dangerous and browbeat human-powered vehicle drivers for daring to use it.

  11. Eric wrote:
    “The planners like to use the ’85th percentile’ rule”

    Kevin’s comment:
    So if enough morons are going at 200 km/hr that becomes the speed limit? Bizarre.

    I prefer a policy that urban roads have to be safe (actual safety) and feel safe (subjective safety) for all road users. This requires the setting and strict enforcement of proper speed limits.

  12. Steve wrote:
    “In BC, quite a few highways have 90km/hr speed limits”

    Kevin’s comment:
    I presume that these are either in rural areas or are limited-access expressways. If we are talking about 90 km/hr down an urban street filled with homes and shops, then I’ve got a problem with that.

  13. In some ways, I was speaking to those of us who have gotten “confident” in our riding skills. In motorcycle riding, the crash percentages go down over time from the first year of riding onwards … except for a bump around year three. Some people believe that time frame is where people get just a bit too confident of their skills and still don’t realize they have plenty to learn and experience …….

  14. Kevin’s comment: “So if enough morons are going at 200 km/hr [124 mph] that becomes the speed limit?”

    Well, it would have to be 15% of drivers going that fast for 200 km/hr to be the 85th percentile. I suspect the police would be on the case for such easy pickings.

  15. I’m not so sure the 85th percentile is to blame. Many roads have had the same speed limits for years. I think it is more attributable to a phenomenon called “normalization of deviance.” Basically, the 5 mph cushion given by the law has become normalized over time, so that 10 mph became the cushion. Given enough time, the normalization has continued to the point where someone speeding 15 mph can be tailgated by a cop because the speeder is going slower than the cop wants to go. I was one of those speeders in a prior life, and it happened all the time. Now I drive the speed limit, and it seems I’m the slowest person on the road.

    • Me too.

      And I’ve noticed this:

      The percentage of motorists that react badly to a bicyclist claiming the lane is much smaller than the percentage that react badly to a motorist driving the speed limit.


      • RTPAOATPSL: Right To Proceed At Or Above The Posted Speed Limit