Speed Reduction Strategies

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Speed Reduction Strategies

• Ali Kamyab, Research Scientist
• Tom Maze, Professor
• CTRE, Iowa State University

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• Started in 1999 to research, test and evaluate
  work zone safety technology
• Originally the states of Iowa, Kansas, Missouri,
  and Nebraska
• 2001 Wisconsin joined
• Expecting Minnesota and Georgia to become members
  soon

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Iowas program

• Focused on rural work zones and on speed
  reduction
• Initially focused on testing technology to
  moderate speeds (tactical level)
• Next provided a broader look at strategies
  (strategic level)
• Policy actions
• Technology applications
• Regulatory/enforcement strategies
• Currently exploring design, traffic management,
  planning, and enforcement issues

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2000 synthesis of speed reduction strategies

• Regulatory and advisory speed limit signs
• Lane width reduction
• Flaggers
• Police enforcement
• Drone radar
• Speed display monitoring
• Rumble strips
• Optical speed bars

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Reports main conclusion
None of the techniques individually are capable
of reducing vehicle speeds to the desired level.
Effective speed reductions will probably involve
some combination of technologies and policies.
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Regulatory and advisory signs

• Advisory signs little impact
• Increased frequency of signs no impact
• Regulatory impact when enforced
• Regulatory signs with strobes some impact

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Lane width reduction

• It matter how the lane width reduction is done
• Cones little impact
• Concrete barriers more impact
• Lane width reduction reduce speed by 0 16
• Lane width reduction may have minimal impact

Richards, S.H., R.C.Wunderlich, and C.L. Dudek,
Controlling Speeds in Highway Work Zones, TTI,
1984 Benekohal, R.F., Kastel, L.M., and M.
Suhale, Evaluation of Work Zone Speed Control
Techniques, TRR 1035, 1985
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Flagging

• Significant impact
• Improves with training of flagger
• 7-13 mph on rural interstates
• 10 16 mph on two lane roads
• 13 mph on urban arterial streets
• Labor intensive
• Fatiguing

Richards, S.H., R.C.Wunderlich, and C.L. Dudek,
Controlling Speeds in Highway Work Zones, TTI,
1984
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Enforcement

• Significant impact
• Stationary squad car reduce 6 to 22 percent
• Circulating patrol car 3 to 5 percent speed
  reduction

Richards, S.H., Wunderlich, R.C., and C.L.
Dudek, Field Evaluation of Work Zone Speed
Control Techniques, TRR 1035, 1985
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Drone radar, Speed monitor display, and Rumble
strips

• Drone radar
• Minimal impact
• Speed monitor displays
• Impact significant at the beginning
• Impact tends to wane with time
• Rumble strips
• Reduction of average speed by few mph

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Optical speed bars

• Reduce the 85th percentile speed and the mean
  speed
• Significant reduction of the standard deviation
  of speed

Source Meyer, E., A New Look at Optical Speed
Bars, ITE Journal November, 2001
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Conclusions

• All technology provides some benefits
• The impact of all technology diminishes with time
• Enforcements impact is consistent with time
• Reduction continues for a short period even after
  enforcement leaves

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Results of state DOT survey (36 agency responses)
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Results of second state DOT survey
28 state responses
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Results of stepped up enforcement experiment
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Iowas Evaluation of the Wizard CB Alert System
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• Why Rural Focus?
• Increased frequency of construction
• Increased congestion
• Aggressiveness of drivers

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• Motivation for Iowa DOT Concern
• Safety (worker and motorist)
• Rural congestion
• Efficiency of operations

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• Wizard CB Alert System
• Designed and patented by Highway Technologies,
  Inc.
• Built and marketed by TRAFCON Industries, Inc.
• Developed at the request of the Pennsylvania
  Department of Transportation

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• CB warning for upcoming delays
• Focuses on trucks most common users of CBs
• Typically heavy trucks represent 30 or more of
  the traffic
• Attempts to moderate speed before reaching work
  zones

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• Evaluation case study
• Moving work zone
• I-35 paint stripping crew
• Warning on channel 19
• Work zone characteristics
• Moving at 25 mph
• Four to five vehicles spread over about one-mile
• Lead vehicle is stripping truck
• Trailing pick-up with flashing board
• CENTERLINE/EDGELINE PAINT AHEAD

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• Wizard CB alert system experiment
• Broadcast at 30-second interval
• Broadcast on channel 19 (only one channel)
• Varied message depending on user response

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• Evaluation questions
• Did truck operators actually receive the message?
• Did the message effectively alert the drivers?
• Data collection challenges
• Moving work zone making speed measurement
  difficult
• No means to stop truck operators to question them

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• Two proxy measures of effectiveness
• Questionnaire administered to truck operators
  upstream at rest area
• Monitor CB channel for truck operator comments
  (in tailing vehicle)

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• Modifying warning
• This is the Iowa DOT. Slow-moving paint
  operation in the right lane of north bound
  Interstate 35. Please use caution.
• This is the Iowa DOT. Slow-moving paint operation
  in the right lane of northbound Interstate 35
  milepost 160 to milepost 170. Please use
  caution.

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• Modifications continued
• This is the Iowa DOT. Northbound drivers on
  Interstate 35, you are approaching a slow-moving
  paint crew in the right lane. Please use
  caution.
• This is an Iowa DOT road work alert. Northbound
  drivers on Interstate 35, you are approaching a
  slow-moving paint crew in the right lane. Please
  use caution.

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• Evaluation results
• CB Radio Comments
• Operators expressed their disapproval over the
  work zone itself
• Many noticed the new and different message
  majority were positive.
• Thats the first time Ive ever heard anything
  like that. I wish everyone would do that. Itd
  make things a lot easier
• Get off my radio. You need to get a regular
  radio station and warn those four wheelers.

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• Rest Area Survey
• How years of profession driving do you have?
• Do you have a CB?
• Did you see the paint crew and, if so, what was
  your first alert?
• Did you hear the CB alert?
• Did you think the alert was effective?
• Was the message annoying?

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• Rest area results
• 94 total interviews
• 88 (94) had CBs
• Of those with CBs, 70 were tuned to channel 19
  (80)
• 59 of those with CB tuned to channel 19 passed
  the paint crew (63)

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• What alerted you first?
• CB Alert Message 24 (40)
• Lights on Trucks 14 (24)
• Signs 10 (17)
• Arrow Board 7 (12)
• Other Truck Drivers 4 (7)
• Total 59 (100)

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• Out of the 59, 44 said they heard the CB message
  (75)
• Out of the 44, 39 (89) thought it was effective
  
• Out of 44, 1 said the message was annoying

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• Example Comments
• This could save accidents from happening
• This alerts everybody. Its a good idea.
• Neat idea! More states should use this!
• A good idea, but sooner (warning) would be more
  helpful.

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• Conclusions
• No hard data was available
• System appears to be effective
• 41 stated CB alert was their first warning
• Generally popular with truck operators
• How the warning is phrased is important

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• Acknowledgements
• This work was sponsored through Midwest States
  Smart Work Zone Deployment Initiative and
  sponsored by the Iowa Department of Transportation

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