According to the Federal Highway Administration (FHWA), a rural roadway departure occurs when a vehicle crosses the edge line or centerline or otherwise leaves the traveled way in a rural area. Virtually all rural roadway fatalities involve a departure, and rural fatalities are disproportionately higher than urban ones.
In fact, a 2018 American Community Survey from the Census Bureau found that while only 19 percent of the U.S. population lives in rural areas, 30 percent of the total vehicle miles traveled in 2018 occurred in those areas. Unfortunately, a whopping 45 percent of all traffic fatalities that year occurred on rural roads, with the fatality rate per 100 million vehicle miles traveled being two times higher in rural areas than in urban ones.
The heightened risk of roadway departures in rural areas is likely due to several factors, including:
- Higher average roadway speeds
- Older drivers
- More wildlife
- Steeper embankments
- More hills and curves
- Less lighting
- More farming vehicles
In addition, deadly rural roadway departures do not just impact people living in rural areas because “even as people move to more urbanized areas, they are still drawn to rural areas for vacations and recreation,” according to the National Center for Rural Road Safety. Essentially, rural roadway departures are a risk to every driver.
3 Main Categories of Crash Types
Two vehicles colliding head-on accounted for 28 percent of rural roadway departure crashes from 2014 to 2016.
A single vehicle rolling over accounted for 30 percent of crash types, making it the leading cause of rural roadway crashes.
Where Rural Roadway Departures Occur
Because rural roadway departure locations often change drastically from year to year, identifying the best places for safety countermeasures is a huge challenge.
“[Rural roadway departures] are happening scattered over tens of thousands of miles of roadway,” said Matthew Enders, Technical Services Manager for the Washington Department of Transportation.
“Zeroing in on any specific location where it’s going to happen is not easy to do. If you address the location that just had a fatality… the odds are really slim that there’s going to be another one in that exact same spot.”
However, FHWA data does reveal some overall trends. A total of 45 percent of rural roadway departures happen on arterial roads, followed by 29 percent on major and minor collector roads, 16 percent on local roads and ten percent on interstate roads.
In addition, 23 percent of fatal crashes in the U.S. happened on horizontal curves in 2015, despite them making up only five percent of roadway miles.
Why Vehicles Leave the Roadway
The key reasons for rural roadway departures can be broken down into four categories:
The main culprit is typically driver error, which includes speeding. Of the 16,411 rural traffic fatalities in 2018, 26 percent were due to speeding-related crashes. This percentage is similar to urban traffic fatalities.
Another major type of driver error is impaired driving, which led to 4,714 rural roadway fatalities in 2018, though fortunately that number is a 23 percent decrease from 2009.
Other error types include drowsy driving and distracted driving, often due to smartphones. In addition, ten percent of rural drivers do not use their seat belt, which can exacerbate the dangers of driver error.
The lack of sidewalks in rural areas means roadways are a space shared by drivers, pedestrians and bicyclists.
When drivers swerve out of the way of these vulnerable road users, as well as animals or other vehicles entering their lane, they are at greater risk of a roadway departure.
Roadway and Environmental Conditions
Rainfall, steep elevations, sharp curves and low light conditions all contribute to rural roadway departures.
Low light conditions are particularly impactful. Though the majority of vehicle traffic occurs during the day, 45 percent of rural traffic fatalities occurred between six p.m. and six a.m. in 2018, when lighting conditions are typically the poorest.
Vehicle Component Failure
Even for the most careful drivers, a component failure may be difficult to foresee and navigate safely.
When a tire blows out or a brake line fails, for example, a driver may not be able to avoid leaving the roadway.
A Systemic Approach
With rural roadway departures occurring at dynamic locations and for such varied reasons, identifying the right safety countermeasures at the right areas requires a systemic approach.
What Is a Systemic Approach?
According to the FHWA, a systemic approach means leveraging data about high-risk roadway features associated with specific crash types to implement the right safety countermeasures cost effectively.
“It really opened my eyes and my staff’s eyes to what our problems are across our system,” said Thomas Mattson, Public Works Director for Humboldt County, California. “The systemic [approach] lets you step back and say, ‘A problem can occur anywhere in my system. What are the probabilities and what are my best methods of stopping that kind of problem across the entire system?’”
By doing this, you can proactively target your investments based on data, rather than waiting for crashes to happen and only focusing on those locations.
How to Get Started
Start by following these six steps outlined by the FHWA:
1. Identify common crash types and risk factors, such as time of day or year
2. Screen and prioritize all potential locations.
3. Select countermeasures to fit each unique location
4. Prioritize projects accordingly
5. Identify funding, then implement
6. Perform systemic program evaluation
“Everybody has some data,” Mattson said. “Use what you have to start. If you have to get more data, go for it, but don’t not do anything just because you don’t think you have enough data.”
Traffic device-monitoring software can also aid in data gathering.
Using a systemic approach, the Minnesota Department of Transportation (MnDOT) proactively enhanced safety on rural roadways by identifying risk factors for serious and fatal crash types. Then, MnDOT compiled a list of potential countermeasures.
30% of total vehicle miles traveled are on rural roads
45% of traffic fatalities occur on rural roads
For example, after a head-on crash report for two-lane rural highways uncovered that 65 percent of fatal crashes featured the driver drifting over the center line, the report suggested centerline rumble strips be added on highways. According to the report, that countermeasure would prevent approximately 15 fatal crashes annually.
While the rural roadway departure fatalities occurred across great stretches of highway, identifying this common driver action enabled the right countermeasure to be selected and lives to be saved.
By leveraging existing data on rural roadway departures, conclusions can be drawn that aid organizations like the MnDOT in avoiding these devastating incidents in the future.
TAPCO | Senior Product Manager
With several years of product and project management experience, Nick is an expert on wrong-way solutions, dynamic curve warning systems, intersection conflict warning systems, overheight warning systems and LED-enhanced signs.
He manages product life cycles from inception to realization and compiles traffic safety market research to drive innovative ITS solutions.