Reiterated in the Accident Report NTSB/HAR-16/01 PB2016-104807 "Multivehicle Work Zone Crash on Interstate 75 Chattanooga, Tennessee, June 25, 2015" adopted on October 17, 2016 and transmitted on November 3, 2016 Notation Number 8730A: The NTSB recently investigated a crash in Cranbury, New Jersey, where a truck driver’s fatigue and speeding in a work zone were causal factors (NTSB 2015a). As a result of this investigation, the NTSB issued the following recommendation to the FHWA, requesting that it:
Amend the Manual on Uniform Traffic Control Devices “Guidance” for work zone projects on freeways and expressways to advise traffic engineers on the use of supplemental traffic control strategies and devices to mitigate crash events involving heavy commercial vehicles.
Safety Recommendation H-15-16 is classified “Open--Acceptable Response.”
The FHWA has indicated that it will “review Part 6 of the MUTCD to clarify or add provisions regarding freeway and expressway work zones and the possibility of queuing due to reduced capacity created by lane closures and the relative placement of the advance warning devices.” The proposed changes are to be included in the notice of proposed amendments for the next edition of the MUTCD, which has a tentative completion date of June 2018. The FHWA stated that it has issued or funded several publications on this subject, including the following:Mitigating Work Zone Safety and Mobility Challenges Through Intelligent Transportation Systems: Case Studies (FHWA 2014).
Safe Trucking Through Work Zones (FHWA 2003).
Guidance for the Use of Temporary Rumble Strips in Work Zones (ATSSA 2013).96
Innovative End-of-Queue Warning System Reduces Crashes Up to 45% (FHWA 2015).
Further, the FHWA smarter work zones initiative, promoted by its 2015 2016 Every Day Counts program, encourages project coordination and technology applications to improve safety and reduce travel delays. Some of the technologies highlighted include variable speed limit systems and dynamically managed work zone traffic based on real-time conditions.
On April 13, 2015, the FHWA, the FMCSA, and the CVSA conducted a national symposium on work zones and large trucks. Representatives from state departments of transportation, NHTSA, the American Association of State Highway and Transportation Officials, law enforcement, academia, and industry participated. The stakeholders developed a draft work plan with potential recommendations to improve work zone safety, including the following (FHWA?FMCSA?CVSA 2015):
Identify best practices through optimal use of law enforcement and commercial trucking resources, assets, and personnel.
Promote the use of work zone safety devices and strategies (truck-mounted attenuators, large truck ingress/egress signs and alert systems, and temporary/portable rumble strips).
Determine technology solutions for work zone and large truck safety (back-of-queue advance warning systems, next generation real-time traveler information systems, roadside/connected vehicle/vehicle-to-infrastructure options, and onboard equipment options).
Identify key research efforts that inform or affect work zone and large truck safety.
Develop and conduct human factors research on effective strategies to reduce distracted driving and speed for drivers of large trucks and to alert motorists of work zones.
Create a group to spur collaboration on a work zone and large truck safety initiative.
• Develop a communications and outreach plan to support symposium actions.
2.7.4 Safety Recommendations
18.104.22.168 Traffic Control Plan.
TDOT had established procedures for executing impact analyses and developing transportation management plans (TDOT 2007). The Chattanooga work zone project included provisions for greater advance warning, end-of-queue protection, transportation management center monitoring, use of law enforcement personnel, increased inspections, training of personnel, and nighttime work.97 The color, dimensions, selection, and placement of traffic control devices in the work zone met MUTCD requirements. The advance warning area had the minimum required 0.5-mile warning distance sign for the left lane closure. “ROAD WORK AHEAD” signs at 3 miles, 2 miles, 1 mile, 1,500 feet, and 500 feet supplemented the required warning distance signs. Overhead DMSs further supplemented the advance warning signs. TDOT special contract provisions required the additional warning distance for interstate lane closures and the use of queue trucks. The transition area had arrow boards to taper the traffic; and the taper distance was 780 feet, which exceeded the minimum distance required.
Although the TDOT traffic control plan included features beyond the minimum requirements established in the MUTCD, it could be improved by implementing speed management strategies to avoid sudden speed reduction and significant speed variance. The MUTCD, section 6C.01 (Temporary Traffic Control Plans), also indicates that temporary traffic control:
. . . should be designed so that vehicles can travel through the temporary traffic control zone with a speed limit reduction of no more than 10 mph. . . . Where restrictive features justify a speed reduction of more than 10 mph, additional driver notification should be provided. The speed limit should be stepped down in advance of the location requiring the lowest speed, and additional temporary traffic control warning devices should be used. (FHWA 2009)
The NTSB concludes that TDOT processes and procedures were consistent with the work zone safety and mobility requirements of 23 CFR Part 630, and its traffic control plan followed the requirements and most guidance in the MUTCD, but the agency and other state departments of transportation would benefit from additional FHWA guidance on the use of supplemental traffic control strategies and devices to mitigate crash events involving heavy commercial vehicles. Therefore, the NTSB reiterates Safety Recommendation H-15-16 to the FHWA.