Work Zone Mobility and Safety Program
Photo collage: temporary lane closure, road marking installation, cone with mounted warning light, and drum separated work zones.
Office of Operations 21st Century Operations Using 21st Century Technologies

Text from 'Speed Reduction Strategies' PowerPoint Presentation

Slide 01

Speed Reduction Strategies

Ali Kamyab, Research Scientist

Tom Maze, Professor

CTRE, Iowa State University

Logo: CTRE - Center for Transportation Research and Education

Slide 02

Midwest Smart Work Zone Deployment Initiative

  • 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

Slide 03

Iowa's 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

Slide 04

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

Slide 05

Report's 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."

Slide 06

Regulatory and advisory signs

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

Slide 07

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% 1
  • Lane width reduction - may have minimal impact 2

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

Slide 08

Flagging

  • Significant impact 3
    • 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

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

Slide 09

Enforcement

  • Significant impact
  • Stationary squad car - reduce 6 to 22 percent 4
  • Circulating patrol car - 3 to 5 percent speed reduction 4

4 Richards, S.H., Wunderlich, R.C., and C.L. Dudek, Field Evaluation of Work Zone Speed Control Techniques, TRR 1035, 1985

Photo of a squad car in front of a 'Road Work Ahead' sign

Slide 10

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

Photo of a speed monitor display along a stretch of highway

Slide 11

Optical Speed bars

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

Photo of an optical speed bar on a highway

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

Slide 12

Conclusions

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

Slide 13

Results of state DOT survey (36 agency responses)

empty cell Applicable NO Applicable YES Effective Ineffective Partially Effective No Information
Regulatory signs 6 28 2 7 10 9
Advisory signs 26 8 2 0 3 3
CMS 16 18 4 2 5 7
Police Enforcement 8 26 18 0 5 3
Ghost police car 32 2 1 0 1 0
Flaggers 32 2 2 0 0 0
Speed display 28 6 2 1 2 1
Drone radar 28 6 2 1 2 1
Rumble Strips 33 1 0 0 1 0
Lane Narrowing 31 3 2 0 0 1
Pavement markings 33 1 0 0 0 1
HAR 32 2 0 0 1 1

Slide 14

Results of second state DOT survey (28 state responses)

Figure 8. Survey Response Regarding Extra Enforcement Effectiveness

Bar Graph: Roughly 82% of the state responders believed that extra enforcement reduces speeds and 70 % also agreed that it improved safety.

Slide 15

Results of stepped up enforcement experiment

Table 2. Interstate 35/80 Work Zone Crash Frequency Comparison: 1999 (No Extra Enforcement) vs. 2000 (Extra Enforcement)
Crash Location, Road Characteristic Crash Frequency
1999 + 2000 +
Non-intersection, no special features 21 13
Non-intersection, bridge/overpass/underpass 7 0
Non-intersection, Railroad crossing 0 1
Non-intersection, other 2 4
Intersection, within intersection 0 1
Intersection, not within intersection but intersection related 0 3
Interchange, ramp 2 2
Interchange, entrance ramp on major road 3 3
Interchange, on major road between ramps 12 0
Interchange, major road at exit ramp 4 4
Interchange, bridge/overpass/underpass 5 1
Interchange, not within interchange but interchange related 2 0
Total 58 32

For the period March-June

Slide 16

Iowa's Evaluation of the Wizard CB Alert System

Map: Detailed map of major highways in Iowa including: I-80, I-380, I-72, I-29, I-35, and I-90

Slide 17

  • Why Rural Focus?
    • Increased frequency of construction
    • Increased congestion
    • Aggressiveness of drivers

Slide 18

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

Slide 19

  • 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

Photo of a Wizard CB Alert System

Slide 20

  • 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

Slide 21

  • 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"

Photo of several work zone vehicles on a highway with stripping truck in the lead

Slide 22

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

Photo of several work zone vehicles on a highway with stripping truck in the lead

Slide 23

  • Evaluation questions
    1. Did truck operators actually receive the message?
    2. 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

Slide 24

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

Slide 25

  • Modifying warning
    1. This is the Iowa DOT. Slow-moving paint operation in the right lane of north bound Interstate 35. Please use caution.
    2. 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.

Slide 26

  • Modifications continued
    1. 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.
    2. 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.

Slide 27

  • Evaluation results
    • CB Radio Comments
      • Operators expressed their disapproval over the work zone itself
      • Many noticed the new and different message - majority were positive.

"That's the first time I've ever heard anything like that. I wish everyone would do that. It'd make things a lot easier"

"Get off my radio. You need to get a regular radio station and warn those four wheelers."

Slide 28

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

Slide 29

  • 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%)

Slide 30

What alerted you first?

empty cell Responses Response Percentage %
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%

Slide 31

  • 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

Slide 32

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

Slide 33

  • 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

Slide 34

Acknowledgements

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

Slide 35

Helikite

Photos of Helikites

Office of Operations