By Darcy Bullock, Jairaj Desai, Jijo K. Mathew, Enrique D. Saldivar-Carranza, Rahul Suryakant Sakhare, Contributing Authors
Reducing commercial truck crashes is a shared vision of all transportation stakeholders.
In 2022, large commercial trucks (single unit and combination trucks) traveled more than 320 billion vehicle miles (VMT), which is a little more than 10% of all VMT, according to the Federal Highway Administration (FHWA).
Approximately 13% of all roadway fatalities that occurred in 2021 involved a commercial truck. In general, human-related factors are the most common causes of truck accidents.
Too frequently, driver inattention is a contributing factor on long rural sections of interstates when there is unexpected stop traffic. Figure 1 illustrates the severity of one such commercial vehicle crash.
The motivation of this research was to evaluate the effectiveness of in-vehicle alerts (Figure 2) to increase situational awareness of drivers in advance of upcoming slow or stopped traffic on the interstate.
In-cab alerts, such as those shown in Figure 2, serve to warn commercial vehicle drivers of upcoming roadway incidents, slowdowns and work zone construction activities.
Driver response was evaluated by measuring the statistical trends of vehicle speeds after the in-cab alerts were received.
Vehicle speeds pre and post in-cab alert were collected over a 47-day period in the fall of 2023 for trucks traveling on interstate roadways in Ohio. Approximately 3,000 instances of trucks receiving alerts and over 800,000 truck waypoints and speeds were analyzed as part of this study.
For each truck that received an in-cab alert, a speed profile was generated by pivoting the analysis off the timestamp at which each alert was received, and observations were made on speed reductions with reference to time of alert receipt.
A control band of negative 5 mph to 5 mph of speed changes was established to account for minor adjustments and outliers in recorded data.
Speed changes outside of that 5-mph band were then included in the analysis. Figure 3 shows a second-by-second summary visualization of observed cumulative speed reductions for each alert type up to 60 seconds after an alert was received.
A central white band, as shown by the Delta Speed Bins legend, corresponds to the control delta speed threshold of negative 5 mph to 5 mph. Over 22% of trucks receiving Dangerous Slowdown alerts had reduced speeds by 5 mph or more 30 seconds after alert.
General trends also showed that in the case of both alert types, the proportion of speed reductions of at least 5 mph are larger than the proportion of speed increases after the alert which illustrates the significant traffic calming potential of this technology.
In-cab Alerts Impact
Analysis of speed changes before and after the alerts were received showed that approximately 22% of drivers receiving Dangerous Slowdown alerts reduced their speeds by at least 5 mph 30 seconds after receiving such an alert.
Segmenting this analysis by speed found that of vehicles traveling at or above 70 mph at the time of alerting, 26% reduced speeds by at least 5 mph.
These encouraging results suggest that in-cab alerts can be an effective tool for increasing driver situational awareness at critical times such as encountering unexpected slow or stopped traffic on rural interstates (Figure 1).
As this technology matures and false alarm rates are reduced, we are optimistic that the proportion of drivers with noticeable response (greater than 5 mph speed reduction) will increase.
Further Deployment
Although this article summarizes the impact of “Dangerous Slowdown” alerts, further analysis has been performed on congestion alerts and reported in “Quantifying the Impact of In-Cab Alerts on Truck Speed Reductions in Ohio.” In addition, a larger study is underway in 2024 on approximately 2,600 miles of interstate in Indiana with results forthcoming in 2025.
In-cab alerts data between Sept. 28 and Nov. 13, 2023, used in this study were provided by Drivewyze. This study is based upon work supported by the Joint Transportation Research Program administered by the Indiana Department of Transportation and Purdue University.
The contents of this paper reflect the views of the authors, who are responsible for the facts and the accuracy of the data presented herein, and do not necessarily reflect the official views or policies of the sponsoring organizations. These contents do not constitute a standard, specification or regulation. RB
Darcy Bullock is the Lyles Family Professor of Civil Engineering and Director of the Joint Transportation Research Program in the Lyles School of Civil and Construction Engineering at Purdue University. Jairaj Desai, Jijo K. Mathew, Enrique D. Saldivar-Carranza, and Rahul Suryakant Sakhare are Transportation Research Engineers in the Lyles School of Civil and Construction Engineering at Purdue University.
