Why has Highway 402 been shut down a second time in just over a month near Sarnia Ontario? The public has been told it is due to extreme heat conditions which have damaged the road surface. While anything is possible and high heat often exists in summertime, it is doubtful that temperatures have been any more extreme than what typically occurs.
In a CTV News article posted on June 23, 2025 it was reported that unsafe road surface conditions occurred in the westbound lanes between Oil Heritage Road and Mandaumin Road. No explanation was provided by the Ontario Ministry of Transportation which is responsible for the highway maintenance. A photo was shown of a surface disruption that appeared to be at the junction of two concrete slabs. It was speculated that concrete expansion due to high heat caused the condition. It is not clear why the expansion would have occurred at this specific site as opposed to any other which should have sustained similar temperature conditions.
No further discussion was made public until July 28, 2025 when CTV news reported that another road surface problem occurred in the eastbound lanes within a few kilometres of the previous problem a month earlier. A photo displaying the surface showed an upheaval which appeared to be on an asphalt surface. Once again the explanation was “extreme heat” caused the problem. Again, it is not clear why this could be true as recent temperatures seemed to be similar to what typically occurs in summertime in the region.
Historically, Highway 402 had its share of unusual road surface problems, In the late 1970s, as Highway 402 was just completed west of Strathroy, a major surface upheaval occurred in the eastbound lanes just at the east end of the newly completed highway. This existed for several kilometres. The problem was blamed on a concrete underlayer beneath the asphalt paving and a long section of the surface had to be torn up and reset. For many months huge mounds of broken concrete and asphalt were seen piled up along side the highway which were eventually disposed of.
In the spring of 2019 the Ontario Provincial government announced a pilot study where they were going to increase the speed limit on several sections of expressways including a section of Highway 402. The limit was going to be increased from 100 to 110 km/h. That pilot study eventually turned into a permanant change along Highway 402.
While this speed limit change was being proposed Gorski Consulting observed that the road surface along several segments of Highway 402 appeared to be substandard. Testing was being conducted by Gorski Consulting in the spring of 2019 along several expressways and it was decided that the testing would include the segment of Highway 402 between London and Strathroy. This testing demonstrated that the surface of Highway 402 was in worse condition compared to other freeways in the region. This finding was reported in a Gorski Consulting website article of February 5, 2020 entitled “Testing Shows Safety Differences in Ontario’s Expressways”.
In another article posted on June 13, 2019 (“Drivers Beware – Road Data Shows Important Differences in 400 Series Highways in Southwestern Ontario”) we provided some details of the testing. A large portion of this article is reproduced below:
Drivers Beware – Road Data Shows Important Differences in 400 Series Highways in Southwestern Ontario
June 13, 2019
Drivers in Ontario have an objective way of comparing the safety of road surfaces. In the most recent series of testing, Gorski Consulting has compared the surfaces of Highway 401 and 402 with interesting, and differing, results.
The testing involved driving a test vehicle along each highway and documenting the amount of disturbance of the vehicle motion. The “Lateral Rotation” or sideways motion, and “Longitudinal Rotation”, or forward/back motion were sensed. This data was collected at 30 second intervals or, at highway speed (110 km/h), for approximately 900-metre distances. The averages of these motions were obtained and these will be reported.
It had been previously noted that vehicle motions under 0.0200 radians per second indicate a good surface, values between 0.0200 and 0.0500 indicate varying degrees of danger that could be hiding a local safety problem, and values above 0.0500 indicate that major road surface problems likely exist throughout the tested road segment. However there are other, complicating factors. When road surfaces become slippery due to rain, snow or ice there are greater chances of causing loss-of-control because of the lower tire force. There are also issues of speed of a vehicle and the traffic volume. Thus motions caused to a vehicle travelling at high speed are of greater concern even though the distrubed motion is lower. Similarly roads that have high traffic volumes have a greater chance of causing loss-of-control incidents simply because there are more opportunities available. The results of pervious testing have been uploaded to the Road Data page of the Gorski Consulting website.
The results of the most recent testing on Highways 401 and 402 are summarized here in a set of three charts, shown below. The first chart shows the data travelling westbound on Highway 401 from London to Tilbury. The second chart shows the data travelling eastbound on Highway 402 from Strathroy to London. The third chart shows the data from travelling westbound from London to Strathroy. Discontinuities in the Highway 401 data are because not all the collected data was analysed because there was too much data and it would be too time-consuming to analyse it all; thus various areas of the highway are shown in the chart.
Even without discussing the details of the charts, a simple, visual, comparison of the magnitude of the peaks in the data should demonstrate the large differences in the road segments.
The differences can be noted in numeric form by summarizing the lateral and longitudinal data for all the road segments on each highway as shown below.
The data for westbound Highway 401 indicates a suface that is generally in good condition although we previously reported that local problems exist. In an earlier article we used the example of a large disturbance in motion that occurred near the Merllin Road overpass, west of Chatham, Ontario.
The data for eastbound Hwy 402 show elevated values of lateral rotation. In particular the segment between 1.425 and 2.342 kilometres east of the Scotchmere Drive overpass provided readings of: Lateral Rotation = 0.0239, Longitudinal Rotation = 0.0156. While these values may not be alarming for low-speed, low-volume roads, their existence on this high-speed expressway should necessitate explanations.
However the real problems become apparent when examining the data for westbound travel on Highway 402. In three of the road segments the lateral rotation rose above 0.0300. Specifically, at the road segment approaching the Olde Drive overpass and for approximately 674 metres west of that overpass, the average lateral rotation was 0.0446. Again, this is a value that should be of some concern because it was obtained on a high-speed expressway rather than just on a low-speed urban road.
The three figures below show the condition of the westbound lanes of if Highway 402 on approach to the Olde Drive overpass as well as justs past it. These photos were taken on May 21, 2019. Clearly the lanes are visibly in poor condition.
While some patching has been conducted there are dangerous areas of missing asphalt located along the lane-dividing line which would cause problems when drivers attempt to change lanes. The collected data does not demonstrate this danger because the test vehicle did not conduct lane changes at the time of the testing.
Highway 402 has not been ridden in the past few years west of Strathroy so the surface conditions are unknown. Consequently it is unknown if the road surface problems alleged to come from “extreme heat” are accurate or if other factors may be at play. Certainly high heat is experienced frequently in summer months along Highway 402 and there is no indication that this season has been much different from previous seasons.
In another article posted by CTV News on July 29, 2025 the Mayor of Sarnia has questioned the accuracy of the extreme heat source. Mayor Bradley was quoted as follows:
“The province needs to investigate. It’s the same contractor. Why is this happening? Because of heat? You can’t tell me they’re building roads that can’t sustain high, high temperatures,”
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