What road surface conditions could make our vehicle go out of control and kill us? That should be an important issue to anyone who travels on any roadway.
Gorski Consulting has been gathering data on this issue for the past 5 years and this has been posted on the Road Data page of this Gorski Consulting website.
How much a test vehicle is “rocked” forward and back or sideways while travelling on a roadway is the data that is collected. The motion of the test vehicle is captured using an iPhone app. Also, multiple, video cameras are used to document the inside and outside of the vehicle along with views of the roadway. The figure below shows an example of the views from 5 video cameras that were used while the road data was being captured in testing on May 5, 2019. This figure shows the area of westbound Highway 401 approaching Union Road.
The above figure shows the situation on Highway 401 near Union Road where the road surface had been laid in concrete in the summer of 2018. The area is still a construction zone as can be noted by the portable concrete barrier along the median.
On May 24, 2019 a small portion of the latest data was uploaded in an article on this website. Subsequently we have been busy analysing more data such that we now have a substantial portion of the westbound Highway 401 documented from London to Tilbury, Ontario. The updated table is now too large to display as a figure in this article however it will be added to the Road Data page of this website.
Although the general focus of the testing was to obtain motion data of the test vehicle that could be compared to the previous testing, we were particularly interested in studying the difference between the new concrete surface of Highway 401 versus the older asphalt surface. We wanted to know if there was any difference in the motion of the test vehicle as it rode over these two surfaces. As may be recalled, the motion data that is captured is the “longitudinal rotation” and the “lateral rotation” of the vehicle. This longitudinal rotation is what would happen if one were to stand at the front of a car, place one’s hands on the front of hood, and press down to cause a rocking of the vehicle, up and down, alternating, at the front and rear of the vehicle. Lateral rotation is what would happen if one stood at the side of the car’s roof and began pushing sideways thus causing the vehicle to rock back and forth sideways.
The motion of the vehicle is documented in terms of radians per second. One radian is equal to 57.3 degrees. From previous testing we had observed that a good quality road would cause rotations up to 0.0200 radians. A moderate quality road that contains some deficiencies would cause rotations between 0.0200 and 0.0500 radians and a poor quality road with significant safety issues would cause rotations above 0.0500 radians.
All the data in the westbound Highway 401 testing of May 5, 2019 produced motion values well below 0.0200 radians indicating that the road surface was in very good condition. This would be expected since Highway 401 carries the largest volume of traffic travelling at the highest speed and it would be expected to have the highest level of service. Yet there were some interesting findings.
Overall, for the full length of Highway 401 where data has been analysed, the average values were: Lateral Rotation = 0.0126, Longitudinal Rotation = 0.0096 radians.
We then looked at four segments of the highway according to whether the surface was asphalt or concrete and the differences are shown below.
In the article of May 24, 2019 we commented that the concrete surface appeared to produce more longitudinal rotation and less lateral rotation. Now that additional data has been obtained this relationship does not appear to hold. What was obvious, as previously noted, was the the speed of the test vehicle affected the results. So for the concrete surface commencing from Southminster Bourne Rd, the test vehicle was travelling in the range of 84 to 104 km/h because it was travelling in a construction zone. This was significantly slower than the 110 km/h speed that was used when travelling on the asphalt surface where there was no construction zone.
It became obvious that the concrete surface could produce substantial lateral rotation once the test vehicle approached the area of Tilbury, Ontario where there was no longer a construction zone and the speed of the test vehicle was increased to 111 km/h. At that point the lateral rotation values increased to an average of 0.0147 radians. While these data are interesting, overall they are all well below the 0.0200 threshold and we would classify this motion as quite low, indicating a good quality road surface.
As we stated before, these results may appear mundane. However they are important in terms of comparing the other roadways where testing was completed and the motions of the test vehicle were much more violent. Thus this data on Highway 401 presents a benchmark, an example of what motion values should be expected on a good quality road surface. It demonstrates that, if required, it is possible to construct any roadway with this level of quality. When other roadways fall short in their performance one can question why that had to be so and whether improvements are warranted.