Cyclist passing actions by drivers of motor vehicles are important to document in detail if we are to understand how we can avoid dangerous interactions when motor vehicles and cyclists come into contact. Knowing this, Gorski Consulting has commenced a detailed study of such passing motions on Colborne St, just north of St James St, in London, Ontario. The study involved the creation a matrix of markers on the road and then taking video of the cyclists and motor vehicles that pass through the markers. This zone of observation takes place over a distance of 50 metres.
Several articles have already been written about this study. Fourteen instances of cyclist passing motions have been identified as shown in the table below. Articles have already been written about the observations from the first two incidents “Apr 14-1” and “Apr 14-2”. We will now proceed to discuss a third observation “Apr 14-8”.
The table below shows the lateral position of the cyclist as he travelled through the 50-metre zone of observation. Thus the cyclist crosses the Zero marker at timecode 01;09;56;50 and then we see that he generally rides in an area that is less than 1.0 metres west of the concrete gutter. Overall his average position is 0.78 metres west of the concrete gutter. This distance appears to be less than the frame shown below where it suggests that the cyclist is riding substantially further from the concrete gutter.
The scenario in the “Apr 14-8” involves a black Audi car which passes a cyclist just before the traffic units reach the area of observation. So the first frame, taken from video, is shown at the top of the article and we can see the front portion of the Audi passing through the Zero marker at the timecode of 01;09;54;14. The figure below shows the same timecode but looking southward, and here we can see that the Audi has already passed the cyclist who has not reached the area of observation. We can note that the Audi has moved well over the roadway centreline. Our analysis indicates that the right front tire of the Audi is 2.90 metres to the west of the concrete gutter of the northbound lane.
In the next figure below we can we the cyclist crossing the Zero marker thus he is just entering the 50-metre zone of observation. Our analysis indicates that the cyclist is riding at 0.85 metres west of the concrete gutter. It also shows that the Audi has already passed the 25-metre marker.
The next figure below shows the position of the Audi at timecode 01;09;56;47 just as the Audi is crossing the 25-metre marker.
In the next figure below we see the position of the cyclist as he crosses the 25-metre marker at timecode 01;10;01;15. At this time the figure shows that the cyclist is located 0.60 metres west of the concrete gutter. The Audi is no longer in view because it has already moved well north of the cyclist.
In the next figure below we can see that the Audi crosses the 50-metre marker at timecode 01;09;58;47. At this time the right front tire of the Audi is located 1.50 metres west of the concrete gutter. So, when the Audi was at the Zero marker it was located 2.90 metres from the concrete gutter so it has moved back into the northbound lane by 1.40 metres.
In the next figure below we see the status of the cyclist as he passes the 50-metre marker at timecode 01;10;05;14. Here the cyclist is positioned about 0.75 metres west of the concrete gutter.
These figures shown above can be used to examine some further details about this scenario. For example, we can calculate the average speeds of the traffic units. With respect to the Audi it took 2.88 seconds to travel the 25 metre distance between the Zero marker and the 25-metre marker. So its average speed within this zone was 8.68 metres per second or 31.3 km/h. Similarly the cyclist travelled the same distance in 4.42 seconds so its average speed was 5.66 metres per second or 20.36 km/h. Thus the difference is speed of the Audi and cyclist was not large at this first half of the observation zone.
In the second half of the observation zone the Audi travelled from the 25-metre marker to the 50 metre marker in 2.0 seconds so its average speed was 12.5 metres per second or 45 km/h. So the Audi increased it speed during the latter portion of the zone of observation. With respect to the cyclist, he travelled the latter 25 metres in 3.98 seconds so its average speed was 6.28 metres per second or 22.61 km/h. So the cyclist also increased his speed during the latter portion of the observation zone.
Changes in speed matter. Drivers of passing motor vehicles develop a sense of when they should pull out to the left to pass a cyclist by judging their own speed as well as the speed of the cyclist. The driver may steer back into the traffic lane based on that expectation. If a cyclist’s speed suddenly increases the driver of the passing vehicle may misjudge when he should steer back into the lane and a potential contact could occur in some rare instances. Such instances are rare because, generally, cyclists cannot generate a very high acceleration in a short distance so the difference in speed of a cyclist would not be expected to be high in such short distances.
The ultimate purpose of this study is to consider what these scenarios may be like once a painted cycling lane is fully created by the City of London. How will the lateral positions of motor vehicles and cyclists change when the painted cycling lane exists? Will there be a greater potential for motor vehicle and cyclist contact? Will the defined cycling lane improve the safety of cyclists? These are the types of questions that need to be studied in an objective and unbiased fashion. It is the intention of Gorski Consulting to write further articles on other passing motions so that some understanding of the issues can be gained by anyone wishing such information.