The Federal Highway Administration lists nine proven safety countermeasures:
Roundabouts
By converting from a two-way stop control mechanism to a roundabout, a location can experience an 82 percent reduction in severe (injury/fatal) crashes and a 44 percent reduction in overall crashes.
By converting from a signalized intersection to a roundabout, a location can experience a 78 percent reduction in severe (injury/fatal) crashes and a 48 percent reduction in overall crashes.
Corridor Access Management
Access management refers to the design, implementation, and control of entry and exit points along a roadway. This includes intersections with other roads and driveways that serve adjacent properties. These entry and exit points can be managed by carefully planning their location, complexity, extent (i.e., types of turning movements allowed), and if appropriate, use of medians or other schemes that facilitate or prohibit access to the roadway.
Areas where effective access management has been implemented have experienced a 5-23 percent reduction in all crashes along two-lane rural highways, and a 25-31 percent reduction in severe (injury/fatal) crashes along urban/suburban arterials.
Backplates with Retroreflective Borders
A project initiated in 1998 by the Insurance Corporation of British Columbia and the Canadian National Committee on Uniform Traffic Control investigated the effectiveness of applying retroreflective tape around the borders of traffic signal backplates. A small number of signalized intersections were treated and followed up with a simple before/after study, which concluded that the enhancement was effective at reducing crashes. A larger number of sites were subsequently treated and a more robust statistical study was performed.
The use of backplates with retroreflective borders may result in a 15 percent reduction in all crashes at urban, signalized intersections.
Longitudinal Rumble Strips and Stripes on Two-Lane Roads
Roadway departure crashes account for approximately 53% of fatal crashes each year on the Nation’s highways. In 2009, 8,780 single-vehicle roadway departure fatalities occurred on two-lane roads. Rumble strips are designed primarily to address the subset of driver error crashes caused by distracted, drowsy, or otherwise inattentive drivers who unintentionally drift from their lane. Since driver error occurs on all roadway systems (including 2 lane roads), rumble strips are most effective when deployed in a systemic application.
Center line rumble strips on rural two-lane roads: 44% reduction of head on fatal and injury crashes.
Center line rumble strips on urban two-lane roads: 64% reduction of head-on fatal and injury crashes.
Shoulder rumble strips on rural two-lane roads: 36% reduction of run-off-road fatal and injury crashes.
Enhanced Delineation and Friction for Horizontal Curves
Recent data analysis shows that 28 percent of all fatal crashes occur on horizontal curves. Furthermore, about three times as many crashes occur on curves as on tangential sections of roadways. These statistics make horizontal curves prime sites for safety improvements.
Early driver perception and appropriate reaction to changes in the roadway greatly improve the safety of the curve. Inconsistent use of warning signs has been identified as an important factor contributing to the high incidence of crashes on curves.
Safety Edge
Vertical pavement edges are a recognized detriment to safety, contributing to severe crashes that frequently involve rollovers or head-on collisions. Studies in some States find that crashes involving edge drop-offs are two to four times more likely to include a fatality than other crashes on similar roads. Providing a flush, unpaved surface adjacent to the pavement resolves the issue temporarily, but the material is often displaced over time, recreating the dangerous drop-offs either continuously or intermittently along the pavement edge. Research in the early 1980s found a 45 degree pavement edge somewhat effective in mitigating the severity of crashes involving pavement edge drop-offs. However, constructing a durable edge was not perfected until the 1990s, and during development it was found that a flatter, 30 degree angle was easier to construct. Additional testing indicated that the 30 degree edge improved the chances of a safe recovery.
Medians and Pedestrian Crossing Islands in Urban and Suburban Areas
Midblock locations account for more than 70 percent of pedestrian fatalities. This is where vehicle travel speeds are higher, contributing to the larger injury and fatality rate seen at these locations. More than 80 percent of pedestrians die when hit by vehicles traveling at 40 mph or faster while less than 10 percent die when hit at 20 mph or less. Installing such raised channelization on approaches to multi-lane intersections has been shown to be especially effective. Medians are a particularly important pedestrian safety countermeasure in areas where pedestrians access a transit stop or other clear origins/destinations across from each other. Providing raised medians or pedestrian refuge areas at marked crosswalks has demonstrated a 46 percent reduction in pedestrian crashes. At unmarked crosswalk locations, medians have demonstrated a 39 percent reduction in pedestrian crashes.
Pedestrian Hybrid Beacon
The pedestrian hybrid beacon (also known as the High intensity Activated crossWalK (or HAWK)) is a pedestrian-activated warning device located on the roadside or on mast arms over midblock pedestrian crossings. The beacon head consists of two red lenses above a single yellow lens. The beacon head is “dark” until the pedestrian desires to cross the street. At this point, the pedestrian will push an easy to reach button that activates the beacon. After displaying brief flashing and steady yellow intervals, the device displays a steady red indication to drivers and a “WALK” indication to pedestrians, allowing them to cross a major roadway while traffic is stopped. After the pedestrian phase ends, the “WALK” indication changes to a flashing orange hand to notify pedestrians that their clearance time is ending. The hybrid beacon displays alternating flashing red lights to drivers while pedestrians finish their crossings before once again going dark at the conclusion of the cycle.
Installation of the pedestrian hybrid beacon has been shown to provide the following safety benefits: up to a 69 percent reduction in pedestrian crashes and up to a 29 percent reduction in total roadway crashes.
Road Diet
The classic roadway reconfiguration, commonly referred to as a “road diet,” involves converting an undivided four lane roadway into three lanes made up of two through lanes and a center two-way left turn lane. The reduction of lanes allows the roadway to be reallocated for other uses such as bike lanes, pedestrian crossing islands, and/or parking. Road diets have multiple safety and operational benefits for vehicles as well as pedestrians, such as:
- Decreasing vehicle travel lanes for pedestrians to cross, therefore reducing the multiple-threat crash (when one vehicle stops for a pedestrian in a travel lane on a multi-lane road, but the motorist in the next lane does not, resulting in a crash) for pedestrians,
- Providing room for a pedestrian crossing island,
- Improving safety for bicyclists when bike lanes are added (such lanes also create a buffer space between pedestrians and vehicles),
- Providing the opportunity for on-street parking (also a buffer between pedestrians and vehicles),
- Reducing rear-end and side-swipe crashes, and
- Improving speed limit compliance and decreasing crash severity when crashes do occur.
I like all of these except the last one. When I was stationed at Ft Knox, KY in the mid-1970s, the road between the post and Louisville was US 31W, known as the Dixie Highway. Or, to those of us who drove along its two-lanes-each-way-with-a-center-strip, the Dixie Die-way. Far too many drivers used the raised center strip as a merging lane, with predictable results. I have always been a rather, ahem, assertive driver, but this road made me nervous.
“…By converting from a two-way stop control mechanism to a roundabout, a location can experience an 82 percent reduction in severe (injury/fatal) crashes and a 44 percent reduction in overall crashes…”
Even if the two-way stop in question experiences a total yearly traffic of three vehicles a month. Yes, even if the intersection is out on the middle of nowhere and farm animals cross the pavement more often than vehicles do, it’s necessary to eminent domain 20 acres of arable farmland and use 500 tons of concrete to set up a series of roundabouts to control traffic.
I call bullshit. This is US civil engineers with too large of a budget and feeling continental envy.
I can vouch from the last hour that shoulder rumble strips are a comfort at night in a snowstorm.
I wonder if roundabouts (“rotaries” in New England) improve safety merely through hyperawareness due to anxiety. I hate the damn things, and I am not a timid driver. They put a lot of cars on a tight curve with everybody merging and unmerging in all directions, and it makes just continuing in a straight line a task that requires thought. Find the right exit while dodging maniacs. On a curve. Yeah.
They may very well be safer? lots of results are counterintuitive, and the more acute the angle at which cars approach each other, the greater the danger. It makes sense. But they sure don’t feel safe at the time.
“I call bullshit. This is US civil engineers with too large of a budget and feeling continental envy.”
Totally agree. If roundabouts save lives, I’m Marie of Romania. I’ve nearly had three crashes on our local roundabout, and I try to avoid the thing whenever possible.