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Home > Intersections > Resources

Intersection Safety Implementation Plan Process

Step 3: Identify Intersection Countermeasure Types to be Considered

Countermeasure Descriptions

Suggested low-cost countermeasures that can be considered and the intersection conditions where these countermeasures can be most cost-effectively deployed are identified in the tables below. The tables provide information for each countermeasure on target crash types, crash reduction factor (CRF), average expected life, and average construction costs. The CRF information was generated primarily from the August 2008 Federal Highway Administration (FHWA) Toolbox of Countermeasures and Their Potential Effectiveness to Make Intersections Safer,¹ other recent FHWA publications,² and input from intersection safety experts and practitioners.

Systematic Approach

The systematic approach countermeasures were developed by integrating available research findings and input from intersection safety experts and practitioners in the Federal Highway Administration intersection focus states.³ A more detailed description of the crash problem and deployment characteristics for each of the these countermeasures can be found in the FHWA report Low-Cost Safety Enhancements for Stop-Controlled and Signalized Intersections.

The basic set of sign and marking improvements for stop-controlled intersections referenced in Table 9 includes:

• Low-cost countermeasures for the through approach:
  • Doubled-up (left and right), oversize advance intersection warning signs, with street name sign plaques.
• Low-cost countermeasures for the stop approach:
  • Doubled-up (left and right), oversize advance "Stop Ahead" intersection warning signs.
  • Doubled-up (left and right), oversize Stop signs.
  • Installation of a minimum 6 ft. wide raised splitter island on the stop approach (if no pavement widening is required).
  • Properly placed stop bar.
  • Removal of any foliage or parking that limits sight distance.
  • Double arrow warning sign at stem of T-intersections.
  • Small, 6 ft. splitter island.

Figure 3 shows the basic set of sign and marking improvements for stop-controlled intersections, including a splitter island.

Figure 3: Examples of Basic Low-Cost Countermeasures for Stop-Controlled Intersections – Double Up Oversize Warning Signs, Double Stop Signs, Traffic Island on Stop Approach (if feasible), Street Name Signs, Stop Bars, and Double Warning Arrow at the Stem of T-Intersections

The other countermeasures in Table 9 (i.e., those not in the basic set of sign and marking improvements category) should be considered to supplement the basic set of sign and marking improvements at those stop-controlled intersections (1) with higher crash frequencies and (2) that possess the physical characteristics that the countermeasure is intended to mitigate.

Information about the J-turn treatment for stop-controlled intersection is shown in Table 10. The J-turn treatment is to be considered primarily at high-speed, arterial, multi-lane highways and only permit right turn in and right turn out as illustrated in Figure 4. It also may be considered at other lower speed intersections such as those in urban areas.

Figure 4: Turn Restrictions at Multi-Lane Highways

Signalized Intersections

The basic set of sign and signal enhancements referenced in Table 11 includes:

• Twelve-inch LED lenses on all signal heads.
• Back plates on all signal heads (optional reflectorized border).
• A minimum of one traffic signal head per approach lane.
• Traffic signal yellow change interval and all red interval timing adjusted to be in accordance with the Institute of Transportation Engineers (ITE) timing standards.
• Elimination of any late night flashing operations.

The basic set of sign and signal enhancements should be applied to all intersections with high crash frequencies. In addition, the other countermeasures listed in Table 11 should be considered at signalized intersections (1) with higher frequencies of crashes beyond the crash threshold for basic countermeasures and (2) that have specific crash types or physical limitations that the countermeasure is intended to address.

Both Stop-Controlled and Signalized Intersections

Table 14: Crash Reduction Factors, Typical Crash Thresholds, Additional Application Factors, and Estimated Implementation Cost Ranges for Countermeasures at Stop-Controlled Intersections with High-Speed Approaches

Countermeasure	Crash Reduction Factor	Typical Urban Crash Threshold	Typical Rural Crash Threshold	Additional Intersection Concern	Implementation Cost Range per Intersection
Lane narrowing using pavement marking and shoulder rumble strips	31%	10 speed-related crashes in 5 years	5 speed-related crashes in 5 years	Free of noise and bicycle issues-single through lane	$20,000 to $40,000
Lane narrowing using pavement marking and raised pavement markers	Unknown but probably less than 31%	10 speed-related crashes in 5 years	5 speed-related crashes in 5 years	Single through lane	$5,000 to $10,000
Peripheral Transverse pavement markings	Unknown	10 speed-related crashes in 5 years	5 speed-related crashes in 5 years		$3,000 to $5,000
Dynamic speed warning sign to reduce speed	30%	10 speed-related crashes in 5 years	5 speed-related crashes in 5 years		$10,000
Slow pavement markings	Unknown	10 speed-related crashes in 5 years	5 speed-related crashes in 5 years		$2,000 to $5,000
High-Friction Surface	25% (All crashes)	10 speed-related crashes in 5 years	5 speed-related crashes in 5 years		$20,00 to $50,000

Comprehensive Approach

Table 15: Crash Reduction Factors, Default Expected Life, and Estimated Implementation Costs for Corridor and Municipal Enforcement Countermeasures

Countermeasure	Crash Reduction Factor	Typical Urban Crash Threshold	Typical Rural Crash Threshold	Additional Intersection Concern	Implementation Cost Range
Corridor engineering, education, and enforcement (3E) improvements on high-speed arterials with very high frequencies of severe intersection crashes	25% of corridor intersection fatal and incapacitating injury crashes	10 or more intersection fatalities	10 or more intersection fatalities	Length of corridor should be in the 5-10 mile range	$1,000,000 per corridor + $100,000 education and enforcement annually per corridor
Municipal-wide 3E improvements in municipalities with high frequencies of severe intersection crashes	10% of all intersection crashes	Top 5 or so municipalities with the most intersection fatalities		Consider density of severe crashes per capita	$500,000 to 1,000,000 + $100,000 to 200,000 (dependent on the size of the city) education and enforcement annually per municipality

Automated red-light enforcement systems detect vehicles that enter a signalized intersection after the signal phase has turned red. The red-light camera system is connected to the traffic signal and to sensors that monitor traffic flow at the crosswalk or stop line. The system continuously monitors the traffic signal. After a specified time from when the signal turns red, any vehicle entering the intersection after that time triggers the camera. One photograph will show a readable license plate. A second photograph typically shows the red light violator in the intersection. Cameras record the date, time of day, time elapsed since the beginning of the red signal, and vehicle speed. Tickets typically are sent by mail to owners of violating vehicles, based on review of photographic evidence.

Enforcement-assisted light systems activate a white light above the traffic signal as the signal turns into the red phase. Officers can be located downstream of the intersection and, using the white light activation, more easily identify and apprehend red light violators.

Traditional Approach

Since the traditional approach addresses the intersections with the highest crash frequencies and/or severities, the most effective crash-reducing countermeasures should be considered for these intersections. These include roundabouts and left turn lanes. These improvements also are among the costliest countermeasures. Individual analyses are required to determine if they are the most appropriate improvements to implement.

Selecting Countermeasures

Selection of the set of countermeasures to consider for inclusion in the implementation plan will depend on a number of factors, such as:

• The size of the crash problem that the countermeasure may impact.
• The cost and CRF of the countermeasure.
• Any major deployment or policy issues associated with the countermeasure.
• Any legislative restrictions affecting the use or deployment of the countermeasure.

Table 18 provides a template for States to use when considering intersection countermeasures. When completing this template, States should include any additional intersection countermeasures it is using or considering.

Intersections proposed for countermeasures listed under the first category in Table 18 – will consider for widespread deployment – eventually will need field inspection to verify that the countermeasure can be implemented and is appropriate at the intersections identified. It may be appropriate to field verify a sample set of intersections where the countermeasure may be deployed before completing the implementation plan to determine if deployment assumptions are acceptable.

Countermeasures listed under the second category in Table 18 – will limit or restrict deployment – may include countermeasures with which a State has no or little experience (e.g., dynamic intersection warning sign systems at stop-controlled intersections). It may be appropriate to consider listing these types of countermeasures in the second category until further experience is gained.

Those countermeasures listed in the first two categories make up the set of countermeasures to consider for achieving the intersection crash reduction goal. For countermeasures that are to be limited or restricted, States should list the specific issues that need to be addressed before wider deployment is considered. This will be helpful in developing the implementation plan. In addition, States should also identify reasons that countermeasures will not be considered (i.e., the third category in the template) for potential discussion among stakeholders during the workshop in Step 6.

Table 18: Template for Documenting Countermeasure Selection

Countermeasure	Consider for Widespread Cost-Effective Deployment	Limit or Restrict Cost-Effective Deployment Until Issues/Concerns are Resolved	Will not Consider Deploying at This Time
Systematic Approach – Stop-Controlled Intersections
Basic set of sign and marking improvements
Installation of a 6 ft. or greater raised divider on stop approach (installed separately as a supplemental countermeasure)
Either a) flashing solar powered LED beacons on advance intersection warning signs and Stop signs or b) flashing overhead intersection beacons
Dynamic warning sign which advises through traffic that a stopped vehicle is at the intersection and may enter the intersection
Transverse rumble strips across the stop approach lanes in rural areas where noise is not a concern and running Stop signs is a problem ("Stop Ahead" pavement marking legend if noise is a concern)
Dynamic warning sign on the stop approach to advise high-speed approach traffic that a stopped condition is ahead
Extension of the through edge line using short skip pattern may assist drivers to stop at the optimum point
Reflective stripes on sign posts may increase attention to the sign, particularly at night
J-turn modifications on high-speed divided arterials
Systematic Approach – Signalized Intersections
Basic set of signal and sign improvements
Change of permitted and protected left-turn phase to protected-only
Advance cross street name signs for high-speed approaches on arterial highways
Advance left and right "Signal Ahead" warning signs for isolated traffic signals
Supplemental signal face per approach
Advance detection control systems
Signal coordination
Pedestrian countdown signals
Separate pedestrian phasing
Pedestrian ladder or cross-hatched crosswalk and advanced pedestrian warning signs
Systematic Approach – Both Stop-Controlled and Signalized Intersections
New or upgraded lighting
Skid resistance surface
Lane narrowing using pavement marking and shoulder rumble strips
Lane narrowing using pavement marking and raised pavement markers
Peripheral transverse pavement markings
Dynamic speed warning sign on the through approach to reduce speed
"Slow" pavement markings
High-friction surface
Comprehensive Approach
Corridor 3E improvements on high-speed arterials with very high frequencies of severe intersection crashes
Municipal-wide 3E improvements in municipalities with high frequencies of severe intersection crashes
Automated red-light enforcement
Enforcement-assisted lights
Traditional Approach
Roundabouts
Left-turn channelization
Other geometric improvements (i.e., elimination of skew, vertical curve)

¹ http://safety.fhwa.dot.gov/intersection/resources/fhwasa10005/brief_8.cfm

² Synthesis of the Median U-Turn Intersection Treatment, Safety and Operational Benefits, FHWA-HRT-07-033, http://www.fhwa.dot.gov/publications/research/safety/07033/index.cfm
Informational Report on Lighting Design for Midblock Crosswalks, FHWA-HRT-08-053, http://www.fhwa.dot.gov/publications/research/safety/08053/
Two Low-Cost Safety Concepts for Two-Way Stop-Controlled Rural Intersections on High-Speed Two-Lane, Two-Way Roadways, FHWA-HRT-08-063, http://www.fhwa.dot.gov/publications/research/safety/08063/
Traffic Calming on Main Roads Through Rural Communities, FHWA-HRT-08-067, http://www.fhwa.dot.gov/publications/research/safety/08067/

³ The FHWA intersection focus states are a set of States with a disproportionate percent and/or number of intersection fatalities in comparison to other States.

⁴ J-turn treatments are also referred to as restricted-crossing U-turn intersection treatments.