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U.S. Department of Transportation
Federal Highway Administration
Subject: ACTION: Work Zone Safety and Mobility
October 24, 2006
From: Original signed by:
Jeffrey F. Paniati
Associate Administrator for Operations
Reply to Attn. of:
To: Directors of Field Services
Resource Center Director and Operations Managers
Division Administrators
Federal Lands Highway Division Engineers

In 1992, the National Transportation Safety Board (NTSB) issued a report titled, Safety Study: Highway Work Zone Safety.1 The report identified a number of work zone safety concerns. Accordingly, the NTSB issued several recommendations to the Federal Highway Administration (FHWA). The majority of these recommendations have been acted upon by the FHWA. A remaining recommendation pertains to commercial vehicles traveling through work zones:

H-92-45: Determine if a combination of efforts, such as speed reductions coupled with onsite enforcement and positive barriers, may be needed at work zones when commercial vehicles are a relatively large percentage of the average daily traffic.

The presence of a relatively large percentage of commercial vehicles in the average daily traffic through a given work zone should be an important consideration when designing traffic management strategies for that work zone. It is generally accepted that the presence of commercial vehicles (specifically tractor trailers) can increase the potential for crashes and the severity of crashes in work zones. There are various reasons for this, such as speed, stopping distance, visibility, vehicular agility, driver awareness, and lane geometry. The purpose of this memo is to provide guidance on the consideration of commercial vehicles during the development of work zone management strategies.

The traffic characteristics and physical features of a work zone site as well as the type of construction planned will influence the selection of appropriate traffic control and safety devices and measures. The presence of commercial vehicles is one of the traffic characteristics that must be considered. The use of speed reduction zones, police enforcement, and positive barriers are just some of the project design variables that can be applied. The presence of commercial vehicles must also be considered in determining other work zone features, such as the best number and placement of signs (including portable changeable message signs) and lane width/geometry and lane restrictions.

In September 2004, FHWA updated the "Work Zone Safety and Mobility" regulations at 23 CFR 630 Subpart J (copy attached). The updated Rule fosters stronger consideration and management of work zone safety and mobility impacts. This update expanded the existing requirement for developing a traffic control plan (TCP) for handling traffic at each work zone to now require the development and implementation of a transportation management plan (TMP) for every Federal-aid highway project. A TMP lays out the work zone management strategies (including a TCP) that will be used for a road project. TMPs present a more comprehensive approach to managing work zone safety and mobility. FHWA personnel should work with their State counterparts to ensure that the presence of trucks is considered in the design of work zone management strategies and the development of TMPs as they implement the requirements of the Rule.

Guidance is available to assist transportation agencies with development and implementation of TMPs:

Existing work zone traffic control reviews, as well as the process reviews required under the updated Rule, provide an opportunity for FHWA personnel to work with their State counterparts to assess how well the above requirements and work zone design criteria are being applied in the field. In reviewing these factors, appropriate consideration should be given to the presence of commercial vehicles.

Although the updated Rule is not effective until October 2007, FHWA personnel should work with their State counterparts to implement the changes as soon as practical. Additional resources related to the Rule, and to support overall work zone management, are also available at http://ops.fhwa.dot.gov/wz/index.asp. Questions should be referred to Ms. Tracy Scriba via telephone at (202) 366-0855.


1 A summary of the report can be read at http://www.ntsb.gov/publictn/1992/SS9202.htm. The full report is available from the National Technical Information Service (NTIS). Report identification is NTSB Report Number: SS--92-02, adopted on 5/12/1992, NTIS Report Number: PB92-917005.

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