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FHWA Home / Safety / Geometric Design / Publications / Mitigation Strategies For Design Exceptions

Mitigation Measures

 

Because of the extremely difficult environmental constraints, Wyoming DOT was faced with design exceptions of large magnitude—both in terms of the length of highway that was affected and the degree of deviation from design criteria. Because meeting all design criteria was neither feasible nor appropriate at this location, the challenge was to make the highway as substantively safe as possible.

Mitigation Measure 1: Advance Signing

A major mitigation measure implemented by the Wyoming DOT was advance signing. Signing with clear, simple messages was provided throughout the project to give drivers adequate warning of the steep grades (Figure 86) and sharp horizontal curves (Figure 87), as well as upcoming safety features such as brake-test areas and runaway truck ramps (Figure 88), discussed later in this section. Both conventional and electronic signing was used throughout the project. The electronic sign shown in Figure 87 is equipped with a radar speed detection device. The message on the black panel below the sign displays SLOW DOWN, when the measured speed of vehicles is too high.

Figure 86.  Signing for the steep grades is provided throughout the project.

FIGURE 86

Signing for the steep grades is provided throughout the project.

Figure 86 is a photo showing a steep grade warning sign behind the guardrail at a curve in the highway.  The sign consists of two elements.  The top element is a diamond-shaped sign with a symbol of a truck pointing to the left and down on a ramp that slopes up from the left to the right, with the legend "7%" underneath.  The bottom element is a horizontal rectangular sign with the words USE LOWER GEAR on two lines.  The sign has a black legend and border on a yellow background.  In the background, adjacent to the highway is a steep rock cut.

Figure 87.  Electronic signing provides enhanced warning for the non-standard horizontal curves.

FIGURE 87

Electronic signing provides enhanced warning for the non-standard horizontal curves.

Figure 87 is a photo of a warning sign composed of several elements.  At the top are two flashing beacons, inactivated in the photo.  Underneath the beacons is a horizontal rectangular sign with the words CAUTION SHARP CURVES AHEAD on three lines.  The sign is yellow with a black border and legend.  Underneath the sign is an electronic message sign, displaying no message in the photo.

Figure 88.  Advance signing for the truck escape ramp.

FIGURE 88

Advance signing for the truck escape ramp.

Figure 88 is a photo showing a horizontal rectangular sign with the words RUNAWAY TRUCK RAMP 1 MILE on three lines, located at a curve in the highway.  The sign has a black legend and border on a yellow background.

Mitigation Measure 2: Truck Brake-Check Area and Other Pullout Areas

Another mitigation measure taken for the steep grades was a designated area where truckers can pull off the highway and check their brakes (Figure 89). In addition to the brake-check area, there are several other pullout areas:

The mitigative safety effect of these pullout areas is that they give drivers a place to completely pull off the roadway if they have car trouble or other difficulties while they are traveling a highway with steep, mountainous terrain.

Figure 89.  Advance signing for the brake-check turnout.

FIGURE 89

Advance signing for the brake-check turnout.

Figure 89 is a photo showing a horizontal rectangular sign next to the highway with the words STEEP GRADE–7% NEXT 5 MILES TRUCK TURNOUT 1500 FEET CHECK BRAKES on five lines.  The sign is yellow with a black border and legend.

Figure 90.  A pull-off area provides tourist information and spectacular views. Several other small turnout areas provide safe places for drivers to pull off the highway.

FIGURE 90

A pull–off area provides tourist information and spectacular views. Several other small turnout areas provide safe places for drivers to pull off the highway.

Figure 90 is a photo showing a pull–off area near the highway.

Mitigation Measure 3: Truck Arrestor System

An innovative mitigation measure that was implemented by the Wyoming DOT was an escape ramp that captures out–of–control trucks with a proprietary arrestor system (Figure 91 and 92). This measure was chosen through the value engineering process. Thirteen methods were evaluated, with five evaluated in depth. The system that was eventually constructed was selected based on its overall improvement to safety, preferable location, fewer environmental impacts, constructability, lower construction costs, and ease of maintenance and repair.

Figure 91.  Runaway truck ramp with arrestor system.

FIGURE 91

Runaway truck ramp with arrestor system.

Figure 91 is a close–up photo showing a runaway truck ramp on the right side of the highway, with concrete barrier on each side.  Between the barriers is a series of cables designed to capture an out–of–control vehicle and bring it to a safe stop.

Before the reconstruction project, a truck escape ramp had been located on the other side of the roadway, near the same location as the new ramp. Trucks that lost control had to cross the opposing lane of traffic to use the ramp. Finding a suitable location on the right-hand side was challenging and with the canyon on this side of the highway, an innovative method was needed for capturing trucks. The end result was a safer ramp that no longer required crossing the opposing lane of traffic.

Figure 92.  Runaway truck ramp. A nearby ramp on the other side of the roadway was replaced because it required crossing the opposing lane of traffic.

FIGURE 92

Runaway truck ramp. A nearby ramp on the other side of the roadway was replaced because it required crossing the opposing lane of traffic.

Figure 92 is a photo showing the runaway truck ramp from a distance.  This perspective illustrates how the new ramp on the right side of the highway allows use of the ramp without crossing the opposing lane of travel.  An older ramp, which is not visible in the photo, was located on the left side of the highway.

Electronic signing is used to alert drivers when the escape ramp is inoperable. When a truck is captured by the arrestor system, a signal notifies local law enforcement personnel, who then activate the flashing beacons (Figure 93). Wyoming DOT maintenance personnel stop truck traffic while the system is being repaired or when snow is being removed.

Figure 93.  Electronic signing provides advance warning when the truck ramp is closed.

FIGURE 93

Electronic signing provides advance warning when the truck ramp is closed.

Figure 93 is a photo of a sign along the highway.  At the top are two flashing beacons, inactivated in the photo.  Underneath is a horizontal rectangular sign with the words RUNAWAY TRUCK RAMP CLOSED 3 MILES AHEAD WHEN FLASHING. The sign has a black border and legend on a yellow background.

Mitigation Measure 4: Climbing Lanes

With the very steep grades, high truck volumes, and limited passing opportunities, climbing lanes (Figure 94) were added throughout the project to improve operations and prevent dangerous passing maneuvers.

Figure 94.  Climbing lane.

FIGURE 94

Climbing lane.

Figure 94 is a photo showing a steep downgrade.  On the uphill side of the highway there is a climbing lane adjacent to the primary travel lane.

Mitigation Measure 5: Guardrail

The steep topography also made it difficult to provide an adequate clear zone to allow drivers who have run off the road to safely recover. Steep grades and horizontal curves are factors that contribute to run-off-the-road crashes, so the Wyoming DOT placed guardrail strategically throughout the project to prevent these crashes.

Figure 95.  Guardrail on the outside of a horizontal curve.

FIGURE 95

Guardrail on the outside of a horizontal curve.

sFigure 95 is a photo showing a curving segment of highway and w-beam guardrail, mounted on wooden posts, and a series of warning signs on the right.
 
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Page last modified on April 1, 2019
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