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Designing for Speed, Congestion, and Delay in the Work Zone. Gerald Ullman Research Engineer Texas Transportation Institute. Work Zone Safety Trends. Work Zone Consequences. 40,000 injuries/year nationally 120 workers killed annually $4.5 billion/year national economic cost.
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Designing for Speed, Congestion, and Delay in the Work Zone Gerald Ullman Research Engineer Texas Transportation Institute
Work Zone Consequences • 40,000 injuries/year nationally • 120 workers killed annually • $4.5 billion/year national economic cost
Some other facts… • 43,500 miles of the National Highway System sees at least one day of work zone activity annually • In summer, we lose the equivalent of 41 million vehicles per day of roadway capacity due to work zones
Speed Management in Work Zones • Enforcement • Speed control technologies
Enforcement considerations • Realistic and “reasonable” speed limits • Adequate coordination between DOT and enforcement agencies • Labor availability
Enforcement • Circulating 2-3 mph • Stationary 3-13 mph • Police Traffic Controllers 2-14 mph • Operation Hardhat ???
Work Zone Speed Control Technologies • Enforcement surrogates • Driver information/feedback • Perceptual methods
Enforcement Surrogates • “Dummy” vehicles ----- • Unmanned radar 0-2 mph • Remote enforcement ----- • Automated enforcement -----
Driver Information/Feedback • Changeable Message Signs (CMS) 0-2 mph • CMS w/ radar 0-6 mph • Speed trailers 2-10 mph • CB Wizard 0-2 mph • Variable Speed Limits 0-5 mph*
Perceptual Methods • Rumble strips 1-6 mph • Transverse markings 0 mph • Narrowed lanes 0-8 mph
Congestion and Delay Management in Work Zones • Increase work zone capacity and efficiency of flow • Reduce traffic demands at work zone bottleneck points • Communicate accurate estimates of delay and congestion expectations
“Get In, Get Out, Stay Out” • 77% motorists prefer long-term repairs, even if delays are more significant • Focus on longer-lasting materials, better construction methods, longer service life horizon • Major constraint: $$
Increasing Capacity • Late-merge or dynamic merge control • Moveable barrier systems • Contractor accountability
Contractor Accountability • Arizona SR 68 (FHWA-HOP-04-032) • $400k incentive pool • Travel times exceeding 27 minutes reduced incentive pool
Reducing Traffic Demands • Working at night and weekends • Full roadway closures • Portable Intelligent Transportation System (ITS) technology
Concerns about Nightwork • Efficiency, quality of work • Safety • Traveling public • Workers • Worker quality of life
Full Roadway Closures • Roadway completely closed, traffic routed to alternative routes • Increases work efficiency • Eliminates traffic/work crew conflicts • Requires high degree of coordination and contingency planning • Impacts off-site difficult to predict and assess
Key principles • Motorists should not be told something they already know • Motorists should never be provided incorrect information (must maintain credibility) • Motorist diversion thresholds: 10-20 minutes delay