Objectives and Strategies for Improving Safety at Unsignalized and Signalized Intersections

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Collage of photo images depicting safety devices that can improve safety.

This key sheet and the accompanying intersection safety strategy guide sheets are companions to the NCHRP Report 500 series on strategies to reduce crashes at unsignalized (Volume 5) and signalized (Volume 12) intersections.

Objectives and Strategies for Improving Safety at Unsignalized Intersections
Objectives Strategies Time Cost
A Improve management of access near unsignalized intersections A1 Implement driveway closures/relocations (HTML | PDF) Medium Moderate
A2 Implement driveway turn restrictions (HTML | PDF) Short Low
B Reduce the frequency and severity of intersection conflicts through geometric design improvements B1 Provide left-turn lanes at intersections (HTML | PDF) Medium Moderate
B2 Provide longer left-turn lanes at intersections (HTML | PDF) Medium Moderate
B3 Provide offset left-turn lanes at intersections (HTML | PDF) Medium Moderate to High
B4 Provide bypass lanes on shoulders at T-intersections (HTML | PDF) Short Low
B5 Provide left-turn acceleration lanes at divided highway intersections (HTML | PDF) Medium Moderate
B6 Provide right-turn lanes at intersections (HTML | PDF) Medium Moderate
B7 Provide longer right-turn lanes at intersections (HTML | PDF) Medium Moderate
B8 Provide offset right-turn lanes at intersections (HTML | PDF) Medium Moderate to High
B9 Provide right-turn acceleration lanes at intersections (HTML | PDF) Medium Moderate
B10 Provide full-width paved shoulders in intersection areas (HTML | PDF) Medium Moderate
B11 Restrict or eliminate turning maneuvers by signing (HTML | PDF) Short Low
B12 Restrict or eliminate turning maneuvers by providing channelization or closing median openings (HTML | PDF) Short Low
B13 Close or relocate “high-risk” intersections (HTML | PDF) Long High
B14 Convert four-legged intersections to two T-intersections (HTML | PDF) Medium High
B15 Convert offset T-intersections to four-legged intersections (HTML | PDF) Medium High
B16 Realign intersection approaches to reduce or eliminate intersection skew (HTML | PDF) Medium High
B17 Use indirect left-turn treatments to minimize conflicts at divided highway intersections (HTML | PDF) Medium Moderate
B18 Improve pedestrian and bicycle facilities to reduce conflicts between motorists and nonmotorists (HTML | PDF) Medium Moderate
C Improve sight distance at unsignalized intersections C1 Clear sight triangles on stop- or yield-controlled approaches to intersections (HTML | PDF) Short Low
C2 Clear sight triangles in the medians of divided highways near intersections (HTML | PDF) Short Low
C3 Change horizontal and/or vertical alignment of approaches to provide more sight distance (HTML | PDF) Long High
C4 Eliminate parking that restricts sight distance (HTML | PDF) Short Low
D Improve availability of gaps in traffic and assist drivers in judging gap sizes at unsignalized intersections D1 Provide an automated real-time system to inform drivers of the suitability of available gaps for making turning and crossing maneuvers (HTML | PDF)
Medium Moderate
D2 Provide innovative signs and markings to assist drivers in judging the suitability of available gaps for making turning and crossing maneuvers (HTML | PDF)
Medium Low
D3 Retime adjacent signals to create gaps at stop-controlled intersections (HTML | PDF) Short Low
E Improve driver awareness of intersections as viewed from the intersection approach E1 Improve visibility of intersections by providing enhanced signing and delineation (HTML | PDF) Short Low
E2 Improve visibility of the intersection by providing lighting (HTML | PDF) Medium Moderate to High
E3 Install splitter islands on the minor-road approach to an intersection (HTML | PDF) Medium Moderate
E4 Provide a stop bar (or provide a wider stop bar) on minor-road approaches (HTML | PDF) Short Low
E5 Install larger regulatory and warning signs at intersections (HTML | PDF) Short Low
E6 Call attention to the intersection by installing rumble strips on intersection approaches (HTML | PDF) Short Low
E7 Provide dashed markings (extended left edgelines) for major-road continuity across the median opening at divided highway intersections (HTML | PDF) Short Low
E8 Provide supplementary stop signs mounted over the roadway (HTML | PDF) Short Low
E9 Provide pavement markings with supplementary messages, such as STOP AHEAD (HTML | PDF) Short Low
E10 Provide improved maintenance of stop signs (HTML | PDF) Short Low
E11 Install flashing beacons at stop-controlled intersections (HTML | PDF) Short Low
F Choose appropriate intersection traffic control to minimize crash frequency and severity F1 Avoid signalizing through roads (HTML | PDF) Long High
F2 Provide all-way stop-control at appropriate intersections (HTML | PDF) Short Low
F3 Provide roundabouts at appropriate locations (HTML | PDF) Long High
G Improve driver compliance with traffic control devices and traffic laws at intersections G1 Provide targeted enforcement to reduce stop sign violations (HTML | PDF) Short Moderate
G2 Provide targeted public information and education on safety problems at specific intersections (HTML | PDF) Short Low
H Reduce operating speeds on specific intersection approaches H1 Provide targeted speed enforcement (HTML | PDF) Short Moderate
H2 Provide traffic calming on intersection approaches through a combination of geometrics and traffic control devices (HTML | PDF) Medium Moderate
H3 Post appropriate speed limit on intersection approaches (HTML | PDF) Short Low
I Guide motorists more effectively through complex intersections I1 Provide turn path markings (HTML | PDF) Short Low
I2 Provide a double yellow centerline on the median opening of a divided highway at intersections (HTML | PDF) Short Low
I3 Provide lane assignment signing or marking at complex intersections (HTML | PDF) Short Low


Objectives and Strategies for Improving Safety at Signalized Intersections
Objectives Strategies Time Cost
A Reduce frequency and severity of intersection conflicts through traffic control and operational improvements A1 Employ multiphase signal operation (HTML | PDF) Short Low
A2 Optimize clearance intervals (HTML | PDF) Short Low
A3 Restrict or eliminate turning maneuvers (including right turns on red) (HTML | PDF) Short Low
A4 Employ signal coordination (HTML | PDF) Medium Moderate
A5 Employ emergency vehicle preemption (HTML | PDF) Medium Moderate
A6 Improve operation of pedestrian and bicycle facilities at signalized intersections (HTML | PDF) Short Low
A7 Remove unwarranted signal (HTML | PDF) Short Low
B Reduce frequency and severity of intersection conflicts through geometric improvements B1 Provide/improve left-turn channelization (HTML | PDF) Medium Moderate
B2 Provide/improve right-turn channelization (HTML | PDF) Medium Moderate
B3 Improve geometry of pedestrian and bicycle facilities (HTML | PDF) Short Low
B4 Revise geometry of complex intersections (HTML | PDF) Long High
B5 Construct special solutions (HTML | PDF) Long High
C Improve sight distance at signalized intersections C1 Clear sight triangles (HTML | PDF) Short Low
C2 Redesign intersection approaches (HTML | PDF) Long High
D Improve driver awareness of intersections and signal control D1 Improve visibility of intersections on approach(es) (HTML | PDF) Short Low
D2 Improve visibility of signals and signs at intersections (HTML | PDF) Short Low
E Improve driver compliance with traffic control devices E1 Provide public information and education (HTML | PDF) Short Low
E2 Provide targeted conventional enforcement of traffic laws (HTML | PDF) Short Moderate
E3 Implement automated enforcement of red-light running (cameras) (HTML | PDF) Medium Moderate
E4 Implement automated enforcement of approach speeds (cameras) (HTML | PDF) Medium Moderate
E5 Control speed on approaches (HTML | PDF) Medium Moderate
F Improve access management near signalized intersections F1 Restrict access to properties using driveway closures or turn restrictions (HTML | PDF) Short Low
F2 Restrict cross-median access near intersections (HTML | PDF) Short Low
G Improve safety through other infrastructure treatments. G1 Improve drainage in intersection and on approaches (HTML | PDF) Medium Moderate
G2 Provide skid resistance in intersection and on approaches (HTML | PDF) Medium Moderate
G3 Coordinate closely spaced signals near at-grade railroad crossings (HTML | PDF) Medium Moderate
G4 Relocate signal hardware out of clear zone (HTML | PDF) Short Moderate
G5 Restrict or eliminate parking on intersection approaches (HTML | PDF) Short Low

Key to the Guide Sheets

Strategy:

Strategy Name

Where to Use:

This contains a brief description of where you might use this particular strategy and under what circumstances.

Details:

This section contains a brief description of the strategy and how it may be applied to address the safety concern.

Key to Success:

This section will discuss some critical things to consider when implementing this particular strategy in order to be successful.

Issues:

This section will discuss various issues that need to be addressed during the implementation process.

Time frame:

Time frames will naturally vary based on numerous factors (agency procedures, number of stakeholders, need for additional right-of-way). The scale is meant as a general guide. One circle indicates a short time frame for implementation perhaps in as little as a few months or up to 1 year. Example short term strategies include signage improvements, signal timing changes, and sight distance improvements. Two circles indicates a medium time frame of 1-2 years. Example medium term strategies include channelization improvements, system-wide signal improvements, and minor geometric improvements. Three circles indicates a longer time frame of over 2 years. These strategies will typically require major construction or right-of-way acquisition.

Costs:

Costs will also vary considerably and are affected by local conditions. Costs are ranked as: low, moderate, moderate to high, and high. The scale is meant to reflect costs relative to the other strategies described in the category (signalized or unsignalized).

Effectiveness:

This section will discuss any research or evaluations that have been done to ascertain the effectiveness of the particular strategy. Three descriptors are used to identify to what degree the strategy has been evaluated:

Proven: Those strategies that have been used in one or more locations and for which properly designed evaluations have been conducted that show it to be effective. These strategies may be employed with a good degree of confidence, but with the understanding that any application can lead to results that vary significantly from those found in previous evaluations. Crash reduction factors reported are typically based on valid research methods.

Tried: Those strategies that have been implemented in a number of locations and may even be accepted as standards or standard approaches, but for which there have not been found valid evaluations. These strategies, while frequently or even generally used, should be applied with caution; users should carefully consider the attributes cited in the guide and relate them to the specific conditions for which they are being considered. There can be some degree of assurance that implementation will not likely have a negative impact on safety and will very likely have a positive one. Crash reduction factors reported are not necessarily based on valid research methods and should be used with caution.

Experimental: Those strategies that have been suggested and that at least one agency has considered sufficiently promising to try on a small scale in at least one location. These strategies should be considered only after the others have been determined to be inappropriate or unfeasible. Even where they are considered, their implementation should initially occur using a very controlled and limited pilot study that includes a properly designed evaluation component.

Compatibility:

This section will make note of any compatibility issues with other strategies.

Supplemental Information:

This section will guide the reader to other information relevant to this strategy such as documents and Web sites.




For more information contact:

FHWA Office of Safety Design
E71, 1200 New Jersey Avenue SE
Washington, D.C. 20590
(202) 366-9064
http://safety.fhwa.dot.gov

FHWA Resource Center – Safety and Design Team
19900 Governors Drive Suite 301
Olympia Fields, IL 60461
(708) 283-3545
http://www.fhwa.dot.gov/resourcecenter

Program Contact

Jeffrey Shaw

708-283-3524

What's New

Signalized Intersections: An Informational Guide

South Carolina Case Study: Systematic Intersection Improvements

Stop-Controlled Intersection Safety: Through Route Activated Warning Systems

Roundabouts: An Informational Guide, Second Edition (NCHRP Report 672)

Roundabouts Peer-to-Peer Assistance

How to drive a roundabout (WSDOT)

Modern Roundabouts: A Safer Choice

Highlights

FHWA's Intersection Resources Library CD-ROM

Roundabouts Technical Summary

Mini-Roundabouts Technical Summary

Access Management in the Vicinity of Intersections Technical Summary

Intersection Safety Case Studies

Intersection Safety Technologies

Presentation: Intersection Safety

Example Intersection Safety Implementation Plan

Intersection Safety Implementation Plan Workshop

Example Data Analysis Package and Straw Man Outline