A detour of the Thames Valley Parkway in London Ontario has caused cyclists to travel through undesirable road conditions such as this narrowing of Talbot Street as it travels through the underpass of the Canadian Pacific Railway line.

Construction detours are a necessity of life. However with the increase in cyclist traffic in North American cities the relatively simple detour route may require new considerations. In previous years, when motor vehicles dominated traffic volumes, there was less need to focus on the qualities of the roadway on which traffic was diverted. However, as cyclist volumes are increased there is a greater need to consider how those cyclists will mix with motor vehicle traffic. Also certain roadway characteristics that may be unimportant to motor vehicle travel may be of great importance to the safety of cyclists.

The Talbot-Grosvenor Detour

An example of the complexity of the problem is demonstrated in the construction detour in London, Ontario that was necessitated when the north branch of the multi-use pathway, the Thames Valley Parkway (TVP), needed to be closed for construction.

The TVP is a shared use facility that allows non-motor-vehicle traffic to travel through London. It generally follows the banks of the Thames River. The area of construction of the TVP is in the north-south section between the Blackfriars Bridge and Western University. Recent traffic counts indicate that about 84 cyclists and 102 pedestrians use the facility every hour. In addition another 7 special users (wheel-chaired, e-scooter, skateboard, etc.) also use the facility every hour.

Employees at the City of London developed a detour of the construction site on city streets that would take cyclists through several challenging roadway features. Three areas of concern can be noted.

Three Areas of Concern

Firstly, the detour required that cyclists make a left-turn to travel northbound on Talbot Street. Although Talbot Street is a two-lane roadway it is very busy and few gaps in traffic would be available for a cyclist to complete such a turn. Traffic volume data from August 23, 2018 available from the City of London indicates an AADT of 14,000.

Secondly, the same detour caused cyclists to travel through the narrowing of Talbot Street as it passed under a narrow underpass of the Canadian Pacific Railway line. And thirdly the detour caused cyclists to travel down a steep downgrade of Grosvenor Street into a busy parking lot at Gibbons Park.

This map shows a view of the Thames Valley Parkway (blue lines) and the detour (orange lines). The three orange circles indicate locations along the detour where challenging conditions exist for cyclists.

Some examples of the challenges existing at the detour are shown in the figures below.

In this example, looking west, a cyclist using the detour approaches eastbound on Ann Street in preparation to making a left turn on Talbot Street (in the foreground).
After some delay, bumper to bumper traffic has come to a standstill allowing the cyclist to make the left turn. However, rather than travelling on the road the cyclist opts to travel on the east sidewalk of Talbot.
Understanding the importance of her safety the cyclist continues riding on the east sidewalk. Rather than endangering herself by riding on the narrowing of Talbot Street she proceeds using the sidewalk underneath the underpass of the Canadian Pacific National Railway line.
In a second example these two riders avoid making the left turn onto Talbot Street by turning onto the west sidewalk, as shown in the next image.
Again the cyclists avoid the dangers of the underpass by riding on the sidewalk. However there is a problem. The west sidewalk on which they ride comes to an end at the underpass. So they must still find a way of crossing Talbot Street before reaching the underpass.
As shown in this northward view, traffic is bumper to bumper at the underpass and the orange arrow at the upper left of this photo shows the sign that warns that the west sidewalk comes to an end. Thus cyclists would have to attempt to cross this line of traffic in order to continue riding northward along the detour.
Looking in the opposite direction (southward), the intersection at Ann Street is shown in the foreground. A solid line of northbound traffic on Talbot would make it challenging for cyclists to enter this line with a left turn from Ann Street.
A further complication is noted here where concrete mixer trucks use Ann Street to come in and out of the concrete mixing plant at the west end of Ann Street. The visibility afforded to drivers of concrete mixer trucks is limited under most circumstances. However it is even more so when the truck is not equipped with convex mirrors at its front corners. This makes it more difficult for the driver to detect the presence of cyclists near the truck.
In this closer view of the front end of the concrete mixer truck it can be seen that it is not equipped with convex mirrors at its front corners. The presence of these trucks in the vicinity of cyclists in the zone of detour should raise some concern. Prior investigation of potential conflicts like this should be required before a detour route is selected.

The third safety issue along the detour is the steep downgrade of Grosvenor Street leading into the busy parking lot of Gibbons Park. The downgrade contained a maximum of 15.7 percent which is a steep slope considering the environs of south-western Ontario. Additionally it became known that construction was supposed to take place at the bottom of the downgrade. A sewer pile was installed and this required that a trench be dug across Grosvenor Street at the bottom of the downgrade. This is precisely at the location where cyclists would reach their highest speeds. The site of the construction is shown in the following photo taken from the parking lot of Gibbons Park.

This view is looking east from the parking lot of Gibbons park. It shows the downslope of Grosvenor Street in the background and the trench that was dug across the road in order to install a new sewer pipe. In deciding the direction of the detour personnel at the City of London ought to have known that construction would take place along this portion of the designated detour. It is not clear why City personnel decided that the detour route should pass through this location where it might pose safety risks to cyclists.

One cannot get into the minds of the persons who decided that this detour route was a reasonable decision. There must be some unknown reason why it was selected despite such safety concerns.

Brief documentations of cyclists travelling down the slope of Grosvenor Street were conducted between August 18 and 22, 2022. These observations showed that one cyclist reached a speed of over 57 km/h at the base of the downslope. While this single observation may not reflect the actions of many cyclists it has been demonstrated in previous testing by Gorski Consulting, at other locations in London, that a large percentage of cyclists reach high speeds on downslopes.

While speed is not the only factor that leads to cyclist collisions (and injuries) it must be noted that high speed is any important factor. This is particularly so at the Grosvenor Street site because cyclists ride into a busy parking lot at the end of the downslope. Drivers pulling into and out of parking spots would not be accustomed to looking for cyclists travelling at high speed toward, and past them. Given the typical actions of such drivers they would be more preoccupied with searching for the parked vehicles around them, to avoid hitting them, such that their focus would be on the very limited area around their vehicle.

A short time after the detour route was officially announced cyclists began to complain about its shortcomings. An alternative route was proposed taking cyclists along the west bank of the Thames River which avoided most of the safety problems of the original route. After some consideration the City announced that both routes would be accepted leaving cyclists to chose between the two. While this decision appeared reasonable it did not recognize that some cyclists would likely be unfamiliar with the area and may not be able to judge for themselves which route should be taken. Directing such inexperienced cyclists through the original detour could create unintended safety consequences. Unfortunately the City’s decision still stands until the construction is completed at the end of September, 2022.


Modes of transportation in North American cities are expected to continue to evolve in the near future as the world responds to a global climate crisis. Mass transit, various forms of e-vehicles, walking and cycling are all expected to push aside the motor vehicle that has dominated transportation for the past 100 years. With these new forms of motion there will be challenges as the road system needs to accommodate them. There will be times when accommodation is not ideal and conflicts will exist. For cyclists it means that travelling on roadways designed exclusively for automobiles is likely to continue for some time into the future even though great strides in changing the system occur. Road construction projects and changes to improve cycling environments will necessitate that cyclists be displaced onto detours that are normally thought of in terms of motor vehicle travel. It takes time to reverse that logic. More and more those who plan detour routes will have to have an understanding of the complexity of the new modes of transportation that are evolving. Those detours will have to consider that all users of the detour need to pass through it with a similar level of safety.