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Intersection Safety

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FM 1960 Median Improvements Program

Original publication: National Roadway Safety Awards: Noteworthy Practices Guide; 2011

Description of Practice

FM 1960 thoroughfare has a daily traffic count of 65,000 vehicles, 50 cross streets, 36 signals, and a driveway density of almost 49 driveways per mile. The crash rate along the corridor had a crash rate 217 percent higher than the statewide average. The Texas Department of Transportation's FM 1960 Median Improvement Project set out to improve mobility and safety along this 8 mile stretch.

Key Accomplishments and Results:

  • Installation of raised-curb medians, channelized left-turn bays, signal improvements, and striping.
  • Reduction in conflict points
  • More efficient traffic operations
  • Law enforcement officials in the area believe the project will reduce crashes and help emergency vehicles reach their destinations along the corridor more quickly
  • Modeling indicates a reduction in travel time by 16 percent, delays by 40 percent, and number of stops by 45 percent

"Two photographs: (1) a street with the following features: raised curb median, a channelized left-turn bay, and striping; and (2) a street with the following features: raised curb median and a channelized left-turn bay"

Contact

Danny Perez
Texas Department of Transportation
713 802-5077
Danny.Perez@tx.dot.gov

Tennessee DOT Establishes Project Safety Office to Expedite the Completion of Intersection Projects

Original publication: N/A

Roadway Safety Issue, Problem, or Gap:

Between 2002 and 2005, Tennessee experienced 777 total fatalities at intersections across the state. In 2005, Tennessee was identified as a Focus State in Intersections by the Federal Highway Administration (FHWA) Office of Safety. A focus state in intersection is defined as one of several states that contribute to having the highest number of intersection fatalities nationwide.

Description of Practice

Following a 2007 Intersection Safety Plan Workshop, the FHWA Tennessee Division and the Tennessee Department of Transportation (TDOT) collaborated to develop an Intersection Action Plan. In 2010, TDOT began implementing the plan with the following process improvements:

  • Institute no-plans contracts to expedite the award of contracts based on pre-established safety requirements.
  • Develop an agreement with TDOT Environmental Division to allow TDOT to submit intersection locations prior to site visits to gain NEPA approval in eight weeks.
  • Develop an Intersection Implementation Guide to standardize the steps for completing intersection projects.

Challenges in Implementing the New Practice

After the plan was developed in 2007, TDOT encountered challenges in the implementation of the Intersection Safety Action Plan, including:

  • Lack of trust in systemic application: TDOT did not want to deploy the action plan without going to every site and reviewing all crash data to identify issues.
  • No true ownership: No TDOT office had the time to implement the plan.

How Challenges Were Overcome

  • In November 2009, the FHWA Office of Safety Intersection Team contacted TDOT and the TN Division to develop a strategy to implement the Intersection Safety Action Plan.
  • The TDOT Project Safety Office was created in 2010. This office implemented the Intersection Safety Action Plan.

Benefits Realized From the Practice

Tennessee has reduced intersection safety fatalities by at least 26% across the state. Tennessee is no longer a FHWA Focus State for Intersections. Furthermore, Tennessee has become more innovative with intersection designs by implementing alternative intersection designs including roundabouts, J-Turns, and Diverging Diamond Interchanges.

Contact

Brian Hurst
Tennessee Department of Transportation
615-741-2208
Brian.Hurst@tn.gov

South Carolina Addresses Intersection Safety through Low-Cost, Systematic Improvements

Original publication: N/A

Key Accomplishments

The South Carolina Department of Transportation (SCDOT) began identifying safety improvements to be deployed systematically at intersections across the State in 2008 as part of the Federal Highway Administration's (FHWA) Office of Safety Intersection Focus State initiative. SCDOT believed these improvements would reduce the number of intersection-related fatalities and serious injuries, which was one of the goals defined in SCDOT's 2007 Strategic Highway Safety Plan (SHSP). As part of this process, SCDOT used a 5-year analysis of statewide crash data to identify high-crash intersections and recommend improvements—primarily signing, pavement markings, and signal enhancements. Based on these findings, a list of 2,204 intersections was compiled in the South Carolina Intersection Safety Implementation Plan (ISIP), and SCDOT sought a contracting mechanism to implement the recommended improvements identified in the ISIP within a three-year time frame.

Following the identification of intersections where countermeasures would be applied, SCDOT developed a unique contract vehicle structured to accommodate the systematic approach proposed in the ISIP. The contract was a single, statewide, three-year contract, renewable each year, which allowed for adjustments to be made to improve the quality of the work in subsequent years. The contract was structured to treat approximately one-third of the intersections identified in the plan each year for 3 years.

Throughout the project, the selected contractor and the subcontractor developed a Field Installation Work Book that contained all pertinent information on installation at a particular site, including final approved drawings, installation checklists, and punch list forms. In addition, the contractor and subcontractor developed a reconciliation spreadsheet to manage multiple crews and to document and verify installed quantities for payment during the course of the fast-paced project. The contractor and subcontractor also used a project management website to provide changes to intersection plans to SCDOT on a regular basis and report on the progress of work performed. The contract defined the minimum requirements of the website; however, the website developed ultimately included additional functionality.

Because 23 USC 120(c) allows certain safety improvements such as signing and pavement markings to be eligible for Federal funding, the project was entirely federally funded. The consistency between South Carolina's ISIP and SHSP and the identification of the projects through a systematic, data-driven process allowed for the projects to be implemented using Highway Safety Improvement Program (HSIP) funds.

Through this project, SCDOT made improvements to more than 2,200 intersections that account for forty four percent of all intersection crashes in South Carolina. In deploying this project, SCDOT employed a statewide, low-bid contract vehicle that allowed for uniform implementation resulted in administrative efficiencies and economies of scale through decreased per-unit prices on bulk purchases.

Results

The project has been successful in terms of its outputs and short timeframe, addressing over 2,200 high-crash-frequency intersections in three years. FHWA plans to evaluate the safety effects of SCDOT's low-cost systematic intersection improvements as part of its Evaluation of Low cost Safety Improvements Pooled Fund Study.

Contact

Joey Riddle
South Carolina DOT
Safety Program Engineer
(803) 737-3582
RiddleJD@dot.state.sc.us

Daniel Hinton
FHWA South Carolina Division
Safety and Operations Engineer
(803) 253-3887
Daniel.Hinton@dot.gov

Maryland Evaluates the Safety Benefits of Modern Roundabout Intersections Compared to Two-way Stop-controlled Intersections

Original publication: Roundabouts – The Maryland Experience: a Maryland Success Story (FHWA-SA-09-018)(PDF, 548kB)

The National Highway Traffic Safety Administration (NHTSA) data show that approximately 733,000 people were injured and 7,196 were killed in intersection-related traffic crashes in 2008. The Maryland State Highway Administration (MDSHA) was concerned about the high number of crashes at some of its intersections controlled by two-way stop signs.

Recognizing that high approach speeds coupled with drivers violating stop-controls can result in crashes, MDSHA converted five rural, two-way stop-controlled intersections experiencing a high incidence of crashes, many with injuries, to single-lane roundabout intersections.

"Photograph of a warning sign showing counterclockwise rotating arrows that indicate a roundabout is ahead"
Figure 1:   Roundabout warning sign
Source: Maryland State Highway Administration (used with permission)

 

"Diagram showing the eight potential vehicle conflict points on a standard two-lane roundabout"
Figure 2:   Eight vehicle conflict points
Source: FHWA Roundabouts: An Informational Guide

 

""Diagram showing the 32 potential vehicle conflict points on a standard two-lane roundabout
Figure 3:   32 vehicle conflict points
Source: FHWA Roundabouts: An Informational Guide

 

Key Accomplishments

As the Maryland experience demonstrates, roundabouts can effectively improve safety and reduce traffic crashes and their resulting injuries and/or fatalities.

Results

The roundabouts installed at these Maryland stop-controlled intersections cumulatively reduced total crashes by approximately 69.1 percent and injury crashes by 88 percent in a three-year period after the roundabouts were installed. During this same period, the fatal crashes were eliminated, falling from three under the stop-controlled intersection design to zero after the roundabouts were installed.

Contact

Mike Niederhauser
Maryland State Highway Administration
tmniederhauser@sha.state.md.us

Street Lights at Urban and Rural Intersections Reduce Late-Night/Early Morning Intersection Crashes in Minnesota

Original publication: Reducing Late-Night/Early Morning Intersection Crashes by Providing Lighting (FHWA-SA-09-017)(PDF, 467kB)

More than 40 percent of intersection fatalities occur during late-night/early-morning hours. Further, the crash fatality rate during the late-night/early-morning hours is as much as three times greater than during the day (Traffic Safety Facts, National Highway Traffic Safety Administration, 2008). Minnesota and Kentucky were concerned about the high number of crashes at some of their intersections during late-night/early-morning hours.

Recognizing that poor visibility at intersections during late-night/early-morning hours can cause crashes, the States of Minnesota and Kentucky installed lighting at 55 intersections experiencing a high incidence of crashes.

"Photograph of a stop sign illuminated by a street light"
Figure 1:   Evening view of stop sign at intersection
Source: Photo by April Armstrong (used with permission)

 

Key Accomplishments

As the states' experience demonstrates, providing lighting can effectively improve safety and reduce traffic crashes and their resulting injuries and/or fatalities during late-night/early-morning hours.

Results

The enhanced countermeasure reduced overall late-night/early-morning crashes across these intersections by a weighted average of 35 percent.

Contact

Susan Zarling
Office of Traffic Safety
Minnesota Department of Transportation
susan.zarling@state.mn.us

Colorado Implements Continuous Green T-Intersections to Reduce the Number of Angle Crashes

Original publication: Continuous Green T-Intersections (FHWA-SA-09-016)(PDF, 634kB)

Angle crashes are among the most severe crashes that occur at intersections, including “T- intersections,” across the United States. Research has shown that a primary reason for the high number of crashes is driver inability to judge gaps in opposing traffic. The Colorado Department of Transportation (CDOT) was concerned about the high number of crashes at some of its rural T-intersections controlled by traffic signals.

Recognizing that inadequate stopping sight distance can cause crashes, CDOT installed continuous green T-intersection (CGT) at two intersections experiencing a high incidence of crashes, many with injuries. (These existing intersections met minimum Manual on Uniform Traffic Control Devices standards). The CGT design allows main line through traffic to pass through a signalized intersection without stopping while eliminating conflicting left-turning vehicular movement.

"Photograph of a T-intersection where the signal-controlled through tlane at the top of a T-instersection was converted to a continuous green T. Labels indentify the stem of the T and note the addition of a dedicated left turn lane for trafffic seeking to turn left from the stem of the T onto the flat (top) of the T."
Figure 1:   Aerial view of the CGT in Grand Junction, Colorado
Source: Photo from Zane Znamenacek, CDOT (used with permission)

 

 

"Photograph of an intersection that was converted to a continuous green T. Photo is taken from the flat of the T on the approach to the intersection, with the stem to the left. The intersection features a dedicated lane for vehicles turning from the stem onto the flat of the T."
Figure 2:   Westbound on US-160
Photo from David Pickren, CDOT (used with permission).

 

Key Accomplishments

As the CDOT experience demonstrates, CGTs can effectively improve safety and reduce traffic crashes (particularly angle crashes) and their resulting injuries and/or fatalities.

Results

The safety enhancements installed at these Colorado signalized intersections cumulatively reduced total crashes by 60 percent, injury crashes by 70 percent, and angle crashes by 96.8 percent per year.

Contact

Zane Znamenacek
Region 3 Traffic Operations Engineer
Colorado Department of Transportation
Zane.Znamenacek@dot.state.co.us

Permissive/Protected Left Turn Phasing in Detroit and Grand Rapids

Original publication: Permissive/Protected Left Turn Phasing (FHWA-SA-09-015)(PDF, 441kB)

Left-turning movements are generally acknowledged to be the highest-risk movements at intersections. An estimated 27 percent of all intersection-related crashes in the United States are associated with left turns, with over two-thirds of these crashes occurring at signalized intersections (O'Connor, T., “Intersection Collision Avoidance Systems Web Page,” California Center for Innovative Transportation, August 2004). The cities of Detroit and Grand Rapids, Michigan, were concerned about the high number of crashes at some of their signalized intersections.

The cities modified the permissive left-turn mode to a permissive/protected mode at 3 intersections experiencing a high incidence of crashes, many with injuries and many due to left-turn head-on crashes.

"Two side-by-side photos of permissive-protected signal heads, with the photo on the left showing the permissive phase (circular green) and the photo on the right showing the protected phase (left-turn arrow)."
Figure 1:   Permissive/Protected Mode
Photo courtesy of Michigan Department of Transportation (used with permission).

 

Key Accomplishments

As the Michigan experience demonstrates, low-cost improvements can effectively improve safety and reduce traffic crashes and their resulting injuries.

Results

The enhanced countermeasure installed at these signalized intersections cumulatively reduced total crashes by approximately 32 percent, injury crashes by 58.9 percent, and left-turn head-on crashes by an average of 84 percent per year.

Contact

Tapan Datta
WSU-Transportation Research Group, MI
tdatta@eng.wayne.edu

Cities of Detroit and Highland Park, MI Implement Low-cost Strategies That Measurably Improved Safety

Original publication: Improving Safety by Providing All-Red Clearance Intervals and Larger Signal Lenses (FHWA-SA-09-014)(PDF, 563kB)

Red-light running is estimated to cause more 170,000 injuries and approximately 900 deaths per year (FHWA, Red-Light Running Web Site). Some of these crashes occur because of driver speeding, distracted driving, or inability or failure to see the traffic control device in time to comply. The cities of Detroit and Highland Park, Michigan, were concerned about the high number of crashes, particularly angle crashes, at some of their signalized urban intersections.

The cities of Detroit and Highland Park implemented all-red clearance intervals and larger signal lenses at 33 intersections experiencing a high incidence of crashes (particularly angle crashes), many with injuries.

""Photograph of a 4-way signal head in which the red light lens is 12 inches in diameter and the yellow and green lenses below it are 8 inches in diameter.
Figure 1: Relative size difference between 12-inch (top lens) and 8-inch signal lens (bottom lenses)

 

"Map of the Woodward Avenue Corridor"
Figure 2:   Site Map of the Woodward Avenue Corridor

 

Key Accomplishments

As the Michigan experience demonstrates, low-cost improvements can effectively improve safety and reduce traffic crashes and their resulting injuries.

Results

The combinations of enhanced countermeasures installed at these Michigan signalized intersections cumulatively reduced total crashes by approximately 33.3 percent and injury crashes by an average of 45.5 percent per year. Angle crashes were reduced by a significant 75.7 percent per year at the treated intersections.

Contact

Tapan Datta
WSU-Transportation Research Group, MI
tdatta@eng.wayne.edu

Minnesota Roundabout - A Scott County Success Story

Original publication: Minnesota Roundabout - A Scott County Success Story (FHWA-SA-09-013)(PDF, 587kB)

Two fatal crashes and 50 injury crashes occurred in a five-year period at the rural, two-way stop, high-speed intersection of Highway 13 and County Road 2 in Minnesota. Attempts to reduce crash frequency with a variety of safety treatments at the intersection (including larger stop signs, striping, and flashing lights) were relatively unsuccessful.

The Minnesota Department of Transportation (Mn/DOT) sought to reduce crashes by converting the two-way stop controlled intersection to a single-lane roundabout. The roundabout was constructed with a central island 110 feet in diameter.

""Photo of the roundabout installed at the intersection of Highway 13 and County Rd 2 in Scott County, MN
Figure 1:   Intersection of State Highway 13 and County Road 2
Photo by Jody K. Hassel (used with permission)

 

"Diagram showing the eight potential vehicle conflict points on a standard two-lane roundabout"
Figure 2:   Eight vehicle conflict points
Source: FHWA Roundabouts: An Informational Guide

 

 

""Diagram showing the 32 potential vehicle conflict points on a standard two-lane roundabout
Figure 3:   32 vehicle conflict points
Source: FHWA Roundabouts: An Informational Guide

 

Key Accomplishments

The Minnesota Department of Transportation (Mn/DOT) sought to reduce crashes by converting the two-way stop controlled intersection to a single-lane roundabout. The roundabout was constructed with a central island 110 feet in diameter.

Results

Converting this intersection to a roundabout resulted in a 76.2 percent reduction in total crashes and a 78.7 percent reduction in injury crashes. Angle crashes were eliminated.

Contact

Anthony Winiecki
Scott County Public Works Department
Jordan, MN
336-747-6867
twiniecki@co.scott.mn.us

Signal Flashing Mode Removed During Late-Night/Early-Morning Operation

Original publication: Removal of Signal Flashing Mode during Late-Night/Early-Morning Operation; FHWA-SA-09-012; 2009 (PDF, 379kB)

For years, it has been standard practice to operate traffic signals in the flashing mode when traffic volumes are low, typically during late-night/early-morning hours. Recognizing that field studies have indicated that crash rates may increase around traffic signals using flashing operations during late-night/early-morning conditions (Source: S.F. Polanis, “Right-Angle Crashes and Late-Night/Early-Morning Flashing Operation: 19 Case Studies,” ITE Journal, April 2002). The City of Winston-Salem, North Carolina was concerned about the high number of crashes at urban signalized intersections operating in the flashing mode during late-night/early-morning hours.

The City of Winston-Salem changed signal operations from flashing mode to steady (stop-and-go) mode during late-night/early-morning hours at 8 intersections experiencing a high incidence of injury crashes, particularly right-angle crashes. The eight intersections ranged in size from one-to-three lanes in each direction, with most being two-lane intersections. All of the intersections had a speed limit of 35 mph (with one 30 mph cross street).

"Early morning photograph of a rural road with non-flashing traffic lights"
Figure 1   Photo by Ron Schaefer (used with permission)

 

"Early morning photograph of a two-lane suburban road with non-flashing traffic lights"
Figure 2   Photo by Vaughn W. Inman (used with permission)

 

Key Accomplishments

As the Winston-Salem experience demonstrates, removing signals from late-night/early-morning flashing mode operation effectively improves safety and reduces traffic crashes and their resulting injuries.

Results

The removal of the late-night/early-morning flashing mode from eight urban intersections in Winston-Salem cumulatively reduced total crashes by 30.9 percent, injury crashes by 60.1 percent, and right-angle crashes by 88.8 percent per year.

Contact

Stanley Polanis
Director of Transportation
City of Winston-Salem, NC
336-747-6867
stanp@cityofws.org