An unintended veering out of a travel lane can be the cause of traffic disruptions that ultimately lead to a collision. Collision Reconstructionists who examine the post-collision evidence are rarely able to detect the physical evidence of such an action because, for the vast percentage of cases, no physical evidence exists.
To get a handle on how often such veering occurs Gorski Consulting has examined the videotaped observations of traffic from four sessions at three sites along Highway 401 in South-western Ontario. As mentioned in previous posts, these videotaping sessions were conducted this past fall using multiple video cameras over a period of 2 hours in each session.
During an initial session on October 30, 2018 it was observed that a substantial number of vehicles were veering to the right, out of the right lane, the drivers would then react and bring the vehicle back within the right lane. An obvious example of this occurrence is shown in the following sequence of still frames taken from the video of a camera positioned on the overpass of Westminster Drive and looking into the westbound lanes of Highway 401.
Thus this became the reason to look at the other sessions and document all those incidents where such veering was observed. The table below is a summary of those observations for the three sites and four videotaping sessions.
Generally one could conclude that about 1 to 2 percent of vehicles in the right lane of Highway 401 will veer out of the lane in an observed distance of about 400 metres.
This can also be expressed in terms of the actual numbers of veering vehicles observed per hour. As noted in the table above the session at Graham Road provided the least number of observations of veering per hour. Only 15 vehicles were observed to veer out of the right lane in a time of two hours. So the frequency would be about 7 to 8 vehicles per hour.
In contrast the two sessions at the Westminster Ave site provided between 36 and 43 observations for two hours or about 18 to 21 veering motions per hour.
The Westminster Drive site is interesting because there is a curve that terminates between the 400 and 300 metre markers of our testing. Historically loss–of-control collisions have been more prominent at the end of such curves. Thus it is not surprising that the Westminster site would generate more veering vehicles because of the presence of the curve.
We have now discussed a number of issues relating to the safety of Highway 401 between Tilbury and London, Ontario. This length of highway is where the new High Tension Cable Median Barrier is being installed by the Ontario Ministry of Transport. In earlier posts we have shown how many large trucks drive through area. During weekdays the percentage of transport trucks may approach 50%. During weekends and holidays that percentage is less. We have also examined the difference in speed between trucks that are limited to a maximum of about 105 km/h and non-trucks that travel at an average speed of 116 to 119 km/h. And we have also presented data indicating that over 18% of drivers allow a gap of less than two seconds between the front of their vehicle and the rear of the vehicle they are following. These are some of the data that provide a glimpse of the safety problem on Highway 401.