Intersection Improvements

General Description:

Geometric and signal timing improvements can improve the traffic flow through an intersection.  These types of upgrades include additional turning lanes, protected turns, Turn Restrictions, lane widening, signal timing optimization and other methods of improving the intersection’s capacity.  Roundabouts are becoming more popular and allow for increased capacity and simplification of some intersections.  Signal coordination amongst consecutive intersections allows platoons of vehicles to travel along a corridor, further improving a system’s efficiency. 

Effects of Solution:

¨ Increase Passenger Throughput

þ Increase Roadway Capacity (Optimized intersections increase capacity)

þ Manage System Efficiency (Delay can be minimized at intersections)

¨ Reduce Local Demand

Proper improvements may increase the capacity of the intersection through additional turn lanes and movements, through lanes, timing improvements, or other means.  By retiming an intersection, the system is managed more efficiently.  Proper allocation of green time to movements that need it will allow traffic to use the intersection more efficiently.

Examples of Implementation:

No specific examples available at the time of publication.

Cost/Financial Information:

Source: A Toolbox for Alleviating Traffic Congestion and Enhancing Mobility, Institute of Transportation Engineers.  (Cost/financial information is estimated, and will vary based on size and scope of project, number of units, etc.)

Intersection improvements may be as simple as placing new signs on the approaches ($1,000) or re-striping; to complete intersection reconstruction with new signals, detection technologies, geometry, and others.  Geometric changes to an intersection may be estimated by viewing the Additional Lanes and Traffic Calming fact sheets.

Signal and Signal Upgrades:		Capital Cost	Operating Cost
	Traffic Signal	$95-115K	$2.4-3K
	Signal Controller	$11-17.5K	$.2-.9K
	Equipment or software updating	$2-10K/signal
	Timing Plan Improvements	$300-400/signal
	Signal Coordination	$5-13K
	Signal Removal	$300-400/signal

Additional Resources:

A Toolbox for Alleviating Traffic Congestion and Enhancing Mobility, available for order at: http://www.ite.org/bookstore/index.asp

Federal Highway Administration publication – Roundabouts: An Informational Guide

http://www.tfhrc.gov/safety/00068.htm

Federal Highway Administration publication - Safety Effectiveness of Intersection Left- and Right-Turn Lanes

http://www.tfhrc.gov/safety/pubs/02089/

Federal Highway Administration publication – Flexibility in Highway Design

http://www.fhwa.dot.gov/environment/flexibility/index.cfm

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