The creation of a detour that involves cyclist traffic needs to take into consideration the typical behaviour of cyclists as well as their capabilities. This observation has been demonstrated in the creation of a detour around the construction at the Thames Valley Parkway (TVP) in London, Ontario.

The TVP is a busy and popular multi-use pathway that meanders through London, generally following the banks of its Thames River. The area of construction was located just north-west of the City’s downtown. The map below shows the area of construction as well as the route of the detour. Several areas of concern were noted along this route. In particular, three areas are highlighted in the map: 1.) a left turn from Ann Street onto the busy Talbot Street, 2.) a passage through the narrow Canadian Pacific Railway underpass just south of Oxford Street, and 3.) a steep downgrade of Grosvenor Street into the busy parking lot at Gibbons Park. Two previous articles have discussed the first two areas of concern.

The present article will focus of the last of the dangers: the downslope of Grosvenor Street into the parking lot of Gibbons Park.

Over the years Gorski Consulting has been monitoring the motions of cyclists riding on downslopes of roads and paths in the City of London. The results of these observations have bee posted in a number of earlier articles. The general conclusion drawn from these observations is that downslopes are related to high cyclist speeds and these high cyclists speeds can be a danger, both to riders, and to those who might interact with them. It would not be surprising therefore that we would express concern when the detour of the Thames Valley Parkway created by the City of London would cause cyclists to travel through such a steep downgrade.

Shortly before the detour was in effect on August 22, 2022 measurements were taken of the downslope on Grosvenor Street as it entered into the Gibbons Park parking lot. Using the nearest intersection (St George Street) as a “zero” reference, painted markers were produced at 25-metre intervals and then a digital level was placed on the road at each marker as shown in the two photos below.

This view, looking west, shows a digital carpenter’s level placed at the 100-metre marker which is about half-way down the slope.
In this close-up view of the carpenter’s level placed at the 150-metre marker it can be seen the the level indicates a slope of 13.0 percent. The highest reading of 15.7 percent was obtained at the 175-metre marker.

While cyclists may have used this route on previous occasions, the problem with the detour is that it would increase the volume of cyclists and thereby increase the likelihood that a collision might occur. At the end of the downslope there was a large parking lot. This lot was used by persons attending the popular Gibbons Park. There is a danger when cyclist speeds are increased as they enter such a parking lot because driver’s of motor vehicles would not necessarily be attentive to their approach. Many drivers would be focused on the local vehicles around them as they moved in and out of their parking spaces. The extent of the potential danger needed some objective evaluation and so this was the reason to conduct observations of cyclists.

This photo is looking east from the parking lot of Gibbons Park and showing the downslope of Grosvenor Street in the background. If cyclists travel too quickly into the parking lot they risk colliding with motor vehicles that are travelling in and out of parking spots. Drivers who are focused on nearby vehicles during the parking procedures do not expect a high speed cyclist to approach their area.

The results of the slope-measuring procedure is shown in the table below. As can be seen the severity of the slope increases as the road reaches the bottom of the slope.

On August 31, 2022 video documentation was conducted of cyclists travelling on the downslope of Grosvenor Street. The documentation occurred between the hours of time of 0946 and 1230 hours, or for approximately 2 and 3/4 hours. Forty cyclists were observed during the time. The table below shows the details of the 20 cyclists who travelled westbound on the downslope. These twenty represent an average of just 7.3 cyclists per hour. At a distance of 225 metres the downslope leveled out and this location was several metres within the parking lot.

As can be seen in the above table there were not many full observations made available. Westbound cyclists reaching the parking lot had a choice of two entrances and we chose to follow those cyclists who took the most popular and direct route along the north portion of the lot. However some cyclists opted to turn left and into the south portion of the lot where there were not cameras. So the speed of some cyclists as they entered the parking lot was not documented. Seven observations are denoted at the 225-metre marker with the words “Into other lane”, meaning their speed could not be documented at this location. This resulted in only 13 remaining observations. Observation #2 occurred before we had a chance to complete our camera set-up so this observation was also incomplete at the 225-metre marker, so this caused a further deduction of full observations, down to just 12.

The table shows that four cyclists were observed to be travelling above 30 km/h. While not many these four would pose a safety problem if moving motor vehicles were in their presence. Particularly Observation #23 where the male rider of a road bike was not wearing a helmet yet he was travelling at the highest speed of almost 39 km/h.

View of cyclist travelling westbound on the downslope of Grosvenor Street on August 22, 2022. The cyclist is approaching the 200-metre marker at the entrance to the parking lot at Gibbons Park. Most cyclists travelled to the right however some chose to turn left into the south portion of the parking lot.


I can summarize the results of reviewing the details of all three areas of concern along the noted detour.

Mercifully, the numbers of cyclists using the detour was diminished compared to the number of northbound cyclists that where observed approaching the area of construction of the TVP near Blackfriars bridge. Before the construction the number of cyclists at the Blackfriars Bridge numbered 39 per hour. Just after the closure of the TVP at Ann Street the number of northbound cyclists at the Blackfriars Bridge was reduced to 24 per hour. This was reduced again at the intersection of Ann and Talbots Streets to just 10.5 per hour. And then the number of cyclists was reduced again to just 7.3 per hour at the Grosvenor Street downslope. One can only imagine what developments could have taken place if the number of cyclists using the detour was not diminished.

As of writing the detour is still in effect and it may be lifted, perhaps near the end of September, or later. This is not a long time since the detour began on August 22nd, 2022. Hopefully the deficiencies that have been highlighted will not result any tragic consequences. However the discussion needs some clear-headed thought. Before a detour in finalized there must be certainty that the behaviour and capabilities of cyclists have been taken into account. One cannot just apply one’s theoretical knowledge or rely on published guidelines that may not necessarily apply to the unique specifics of an individual site. A solid understanding of cyclists and their expected actions in needed but also observational data at the site should be gathered as a way of monitoring for problems that may not be apparent at the commencement of the detour.