How the Wyoming DOT Uses GIS to Reduce Truck Blow-Over Crashes on Interstate Highways

In less than six months, the Wyoming Department of Transportation (WYDOT) has developed and implemented a GIS solution to help prevent high-profile vehicle blow-over crashes on the state’s highways. 

Wyoming is home to three major interstates, two of which run coast to coast, and one which connects Wyoming to Colorado and New Mexico from north to south. All three regularly endure severe weather. In fact, just four days after the last major section of I-80 was completed in October 1970, it was closed due to heavy winter snow.

These three interstate highways serve as national truck routes, with I-80 carrying close to 14,000 vehicles a day, 50 to 80 percent of which are trucks. Weather of a different kind causes particular problems for these interstates, in that high winds and vehicle blow-over crashes have been common and increasingly prevalent. Across the 2020–2022 period, these crashes have averaged at almost 170 a year.

Because of the disruption caused by these crashes, the state’s Joint Committee on Transportation, Highways, and Military Affairs raised the issue as a serious concern at the end of May 2023. In less than six months, using a combination of research undertaken by Dr. Noriaki Ohara, associate professor at the University of Wyoming’s College of Engineering & Physical Sciences, and geographic information system (GIS) software from Esri, the Wyoming Department of Transportation was able to develop an intelligent solution to this unique challenge.

Communicated through a variety of media, the solution developed by the Wyoming DOT now provides real-time alerts to commercial vehicle (CV) owners and operators and introduces weight-based rather than blanket road closures. Implemented in line with weather conditions, these alerts target lighter high-sided vehicles more likely to be affected by high winds and strong gusts. First results have been impressive, and the DOT hopes to help further ensure compliance by introducing a system of fines and other sanctions designed to deter drivers who might otherwise be inclined to try their luck.

Several factors have contributed to the increased number of blow-overs. Shifts in the weather itself as a result of climate change have led to more variable, frequent, and severe winds. There have also been changes in driver characteristics, with some less experienced motorists on roadways, and in some cases, driver complacency. Anecdotal reports detail trucking companies encouraging drivers to ignore closures while promising to foot the bill in the event a driver is fined. Additionally, the nature of the trucks themselves has changed, with a greater prevalence of lighter vehicles that aim to save costs on fuel. This has made these newer, less sturdy trucks more prone to blow-overs (which can also have the effect of complicating and extending the times needed to clear incidents).  

Finally, the opening of several distribution centers in and around Cheyenne, the state capitol, has resulted in more vehicles running without goods on board their return trips. “It’s not the heavy, fully loaded trucks that tend to tip over,” says Nick Graf, geospatial project manager at the Wyoming DOT, “it’s the empty trucks returning to the centers that are really problematic.”
 

Historically, the DOT’s road closures have targeted light, high-sided vehicles when winds exceed certain speeds, but Graf adds that interpretations of “light, high-profile vehicles” can vary, especially among drivers who are paid by the mile or per delivery, in which case the commercial imperative often wins out.

Following the Joint Committee meeting in June, the DOT received a briefing focused on Dr. Ohara’s research on the physics of blow-over crashes in July of 2023. The DOT met with and secured the consent of the Wyoming Trucking Association in August for the new approach to road closures, and the first weight-based road closure was issued on October 25.

What the work has done is remove ambiguities by creating a better understanding of the many variables at play. Ohara’s research focused on data from the weather station on I-25 at Wyo Hill, a stretch of road to the south of Cheyenne, but was readily capable of being extrapolated across the state’s road networks by the WYDOT GIS team. This was the key to being able to rapidly expand the new service’s influence.

In particular, the research concentrated on enclosed tractor-trailer combinations. For different wind directions/speeds and vehicles of differing heights, widths, and weights, a series of cones of risk were calculated. The cones, which are drawn perpendicular to vehicles’ sides, widen out as wind strengths increase. They show the angles of susceptibility to blow-over of the vehicles studied. Unsurprisingly, large, lightly loaded vehicles are rendered unsafe before densely loaded ones of the same physical sizes.
 

Armed with the research from Dr. Ohara, the team at WYDOT turned to GIS to begin building the warning system. The team used ArcGIS Pro to combine real-time meteorological data with information on roadway characteristics at locations throughout the state. To begin, accurate weather information is paramount. The WYDOT team chose to use only its own weather-monitoring stations—there are 94 statewide—to support the new CV safety solution. This is because although there are other weather-monitoring facilities in the state, they are not sited close enough to the highway to provide sufficiently accurate and meaningful data. To identify critical locations along the highway, blow-over crash data from 2018–2022 was analyzed. This gave “pretty good” coverage, according to Graf, but there were locations with fewer sample points. Therefore, road surveys were carried out two miles upstream and downstream of each weather station, and for two miles upstream and downstream of every 1/10-mile point on the highway.
 

Through a contract with Cyclomedia, and using its Street Smart service, WYDOT acquired lidar information to build an accurate picture at key locations of the superelevation data (cant angles), which enables vehicles to maintain speed in bends. These locations have been found to increase the potential for blow-overs, even with heavier vehicles. The geometric functions within ArcPy were employed to normalize the lidar information for each location. Road azimuth data was also brought together in order to better appreciate the effects of the angles at which winds are likely to strike moving vehicles. Azimuth-based cone of travel data was combined with Ohara’s cone of risk information. This meant applying the cone of risk data at 90 degrees to the azimuth data and then calculating the wind/weight values. Wind gusts were modeled in the research at 150 percent of the sustained wind speed. The values were recorded in a series of tables that are specific to each weather station/road location. Threshold wind speeds are the result—the points when interventions by the TMC staff are deemed necessary. WYDOT has developed the ability to spatially represent the data, enabling visualization and utilization on live feeds for both public and private consumption.

With the new solution, Transportation Management Center (TMC) staff are now able to respond to weather events quickly, with updates occurring within 15 minutes of weather changes.
 

Various media are used to communicate road status and closure information to the traveling public. WYDOT has a commercial vehicle operator portal and video feeds on social media. There are roadside variable message signs and in-vehicle solutions—a legacy from the 2015 I-80 Commercial Vehicle Pilot Data Exchange (SDX). SDX pushes real-time data directly into vehicles over large geographical areas while maintaining a low terrestrial technology footprint.
 

At the same time, message content is evolving. Greater detail is being added, with more specific weight restrictions being communicated. For example, at a certain location and time, and under certain conditions, only vehicles under 40,000 lbs. may be restricted from operating. WYDOT is working to further integrate with other systems, such as the 511-traveler information hotline and application. Another future aim is the creation of a self-evaluation solution through which users can enter their vehicle type/weight/characteristics and find out which restrictions will apply to them personally. Some further spatial variables will then need to be brought into play, such as vehicle height above the road. “We’re also going to look at wind direction increments,” said Graf. “It may be that the 15-degree increments we’re using at the moment aren’t detailed enough, and we need to go to 5-degree. It may also be that they’re too much, and we need to go to 30-degree.”

WYDOT has successfully worked with the state legislature to bring about a new enforcement regime. A present penalty of a $750 fine, up to 30 days in prison, or both, would be replaced by a $1,000 fine, up to 30 days in jail, or both for the first offense. For the second offense within three years, the fine would be increased to $2,500. It would also have a reckless driving citation, which carries a possible license revocation. The aim is a ‘stick’ approach that encourages drivers to take matters more seriously and for haulers to realize that fines are more than just an occasional business cost. In the period from the first message in October 2023 to the end of February 2024, only seven blow-overs were recorded. And blow-over reductions have been achieved using just wind and wind gust information. Of the seven, two were in previously unidentified areas, and five were violations. This proves the need for a ‘stick’, says Vince Garcia, GIS/ITS/TMC program manager, but also underlines that the information being provided is being taken seriously. “From an engineering perspective, we need a couple more years’ data to see how effective this has been—that, and the new enforcement legislation in place,” continued Garcia. In reality, he notes, it is still early days. “We’re not fine-tuning using the spatial data at present,” said Graf. “We’re only now moving to a point where the TMC can monitor and compare, and then we can implement that too.” The encouraging results of their GIS solution have led the WYDOT team to seek further collaboration with neighboring and peer organizations that face similar high-profile vehicle safety issues.