This article presents an example of a traffic conflict at the site of the Blackfriars Bridge Traffic Study in London, Ontario. Its intent is to explain how such traffic conflicts can be identified and analysed using the video data that has been obtained in the traffic study.
This example involved a northbound female cyclist riding on the Thames Valley Parkway (TVP) and approaching the pedestrian crossing zone at the east end of Blackfriars Bridge. At the same time an eastbound passenger car was crossing Blackfriars Bridge and approaching the pedestrian crossing at the TVP. The incident occurred at approximately 1632 hours during Session #2 on June 17, 2022.
With respect to the car, video cameras captured its travel passing by several markers painted on the road. This allowed the calculation of the vehicle’s speed at several distances approaching the crosswalk. Similarly, video cameras also captured the cycle crossing several markers and speeds of the cycle could also be obtained on approach to the crosswalk.
The photo below shows the cyclist passing the painted marker at 20 metres south of the pedestrian crossing.
The cyclist is then observed passing the marker at 10 metres south of the crossing, seen in the photo below,
It took 2.27 seconds for the cyclist to travel the 10 metre distance between the 20 and 10-metre-markers and therefore her average speed over that distance was 4.41 metres per second (m/s) or 15.86 kilometres per hour (km/h).
In the above photo it can be seen that the cyclist has her head turned slightly to the left and it would be expected that she might be looking for approaching traffic on the road. At the same time there is a pedestrian walking on the sidewalk within her line of sight and this pedestrian may have provided some blockage of her view of traffic on the road.
The photo below shows an eastward view along Blackfriars Bridge and we can see the approaching car which is positioned at the “10-metre-west” marker, or 10 metres west of the west edge of the pedestrian crossing. Note that same pedestrian can be seen on the sidewalk.
Looking at the car’s speed we noted that it was travelling at 24.19 km/h between the 60 and 35-metre-markers. It then reduced its speed to 22.90 km/h between the 35 and 10-metre-markers.
The photo below now shows the cyclist at the south edge of the pedestrian crossing. We noted that, between the 10-metre-marker and the south edge of the road her average speed was 13.19 km/h. Her speed was reduced further to 12.15 km/h in the distance she travelled through the pedestrian crossing. Given the small speed loss it is likely that this occurred from typical rolling resistance rather than from any braking.
Within the distance of 10 metres of approach to the west edge of the pedestrian crossing the car’s average speed was 18.27 km/h. While this is a reduction in speed of about 3.5 km/h from the previous segment the speed loss is not large. There is a substantial upslope of the road at this location so the speed loss could be from that source.
The photo below shows a view looking east at 35 metres west of the pedestrian crossing. Here we can see the taillights of the car and the brake lights are not illuminated.
Another view from the rear of the car is shown below as the cyclist travels across the vehicle’s path. Again no brake lights are illuminated.
In the next two photos we can see the gap between the front of the car and the left side of the cycle as the two units pass by each other.
The pedestrian crossing is 3.92 metres wide and the cyclist is riding generally in the middle of the crossing so it is about 2 metres away from the west edge of the crossing. Yet the shadow from the front end of the car shows that it has crossed over the west edge of the pedestrian crossing. So the front end of the car must be slightly less than 2 metres away from the cyclist as the two units pass each other. Yet, as mentioned before, there is no evidence of braking by the driver whose vehicle travels at an average speed of 17.21 km/h or 4.78 m/s within the pedestrian crossing. At this speed of 4.78 m/s the front end of the car, positioned where it is shown in the above photo, could reach the location of the cyclist in less than 2 metres or less than 0.4 seconds. So this has to be viewed as a “near miss” or a collision that was just barely avoided.
We would want to search for instances like these in the video analysis. What is the probability that a collision could occur at this location and what could be the consequences of such a collision?
The summary table below was shown in a previous article and provides the broad numbers of traffic units documented during our three Sessions.
The total number of eastbound vehicles passing through the site was only 346 over the period of 6 hours of documentation, or about 57.7 vehicles per hour. This is a low volume and one might be quick to suggest that dangers of a collision involving a motor vehicle are likely low. Yet the above table also shows that 1290 other units comprised of cyclists, pedestrians and non-pedestrians were also documented in that 6 hour period, or about 215 units per hour. Thus the volume of the non-motor-vehicle units is almost four times as large as the number of motor vehicles. Thus the argument could be made that, although few motor vehicles exist, when the do exist they are likely to encounter these other units. These other units are much more likely to be injured if a collision occurs. Thus this risk and danger needs to be kept in mind when considering the suitability of allowing motor vehicle traffic on the Blackfriars Bridge.
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