WSDOTUW Road Roughness Study - PowerPoint PPT Presentation

Title: WSDOTUW Road Roughness Study


1
WSDOT/UW Road Roughness Study

• Research Study By
• Kevan Shafizadeh
• University of Washington
• Presented By
• N. Sivaneswaran (Siva)
• Pavement Management Engineer
• Washington State Department of Transportation

2
Study Motivation

• A 1997 telephone survey of 508 Washington adults
  ranked poor road surface/potholes/ruts as the
• second biggest problem with Washington
  interstates
• (second only to congestion/inadequate capacity)
• Source Washington States Joint Legislative
  Audit and Review Committee (JLARC)
• Over 400 million of the state transportation
  budget is devoted to highway maintenance and
  preservation each year.

3
Study Characteristics

• WSDOT sponsored research conducted by University
  of Washington
• Identify factors that affect the publics
  perception of road roughness
• Identify acceptable ride quality thresholds
• When should a pavement be rehabilitated due to
  roughness?

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Pavement Roughness Thresholds(Interstate
Facilities)
Source Federal Highway Administration (FHWA),
1999.
5
WSDOT IRI Determination

• High speed profiler
• Travels at posted speed
• Conducted annually
• All state highways
• Both directions on divided highways
• One direction on simple two way

6
Study Details

• Phase I Customer Survey
• Mailout-Mailback Survey
• General customer satisfaction
• Phase II In-Vehicle Study
• 40 road segments
• I-5, SR-520, I-90, and I-405

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Phase I Customer Survey

• General opinion about roughness, road quality
  issues around Seattle area
• Collected individual socio-demographic
  information
• Gender, Age, Income, Education, etc.
• Willingness to participate in a driving
  experiment?

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Phase I Customer Survey

• License plates were recorded of vehicles entering
  and exiting SR-520 near UW
• Surveys were mailed out to individuals through
  the WA DOL with return postage
• Completed surveys were mailed back to UW

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Phase I Customer Survey

• Over 2,800 license plates collected (Fall 2000)
• 2,570 surveys mailed to registered owners
  (Winter 2000)
• 529 Valid Surveys Returned
• 173 Valid Surveys with Contact Info

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Phase I Customer Survey

• General customer satisfaction information
  obtained from Seattle-Area commuters

Note Results based on 1-5 scale where 1
excellent, 3 average, and 5 poor.
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Summary Statistics Gender
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Summary Statistics Income
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Summary Statistics Age
14
Summary Statistics Education
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Phase II In-Vehicle Surveys

• Individuals were surveyed for their perceptions
  of roughness while driving on 40 local freeway
  segments, controlling for
• In-Vehicle Noise
• Vehicle Type
• Vehicle Speed
• Pavement Type
• Start Location
• Weather Conditions
• Roughness (IRI)

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Phase II Segment Selection Criteria

• Freeway segment in Seattle study area that
• Is easily and safely traversable by drivers of
  varying abilities and in a reasonable amount of
  time (lt 2 hrs)
• Has consistent and homogenous attributes
• Same Surface Type
• Same Geometric Design ( of Lanes, Shoulder
  Widths)
• Same Terrain
• Similar IRI
• Is separated by distinguishable and has easily
  identifiable features
• Corresponds to locations where physical indices
  have been documented (Washington State Pavement
  Management System (WSPMS))
• Samples a range of IRI values

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Study Vicinity
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Study Loop
University Village
Eastgate PR
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Summary of IRI Measurements
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In-Vehicle Participants

• 56 individual drivers
• 2240 driver-segments observations
• Four different vehicle types
• Midsize sedan - KIA Optima (18 participants
  32)
• Sport utility Jeep Grand Cherokee(16
  participants 29)
• Pickup Ford Ranger(12 participants 21)
• Minivan Ford Windstar(10 participants 18)

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Results Roughness Rankings vs. IRI
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Results Roughness Rankings vs. IRI
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Roughness Ranking vs IRI
5
5.0
4.5
4.0
4
3.5
3.0
Mean Perceived Roughness Ranking
Measured IRI (m/km)
3
2.5
2.0
1.5
2
1.0
0.5
1
0.0
Mean Rank by Drivers (1smooth, 5rough)
Measured IRI (m/km)
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Roughness Ranking vs IRI(elevated segments)
5
300
250
4
200
Mean Perceived Roughness Ranking
Measured IRI (in/mi)
3
150
100
2
50
1
0
Roughness Rankings on Elevated Segments
Measured IRI (in/mi)
Roughess Rankings on Non-Elevated Segments
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Roughness Ranking vs IRI (by pavement type and
elevated segments)
5
300
250
4
200
Mean Perceived Roughness Ranking
Measured IRI (in/mi)
3
150
100
2
50
1
0
Roughness Rankings on PCCP Segments
Measured IRI (in/mi)
Roughness Rankings on ACP Segments
Roughness Rankings on Elevated Segments
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Acceptability Thresholds
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Acceptability Thresholds
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Acceptability Thresholds
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Results Statistical Models
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Study Conclusions

• IRI does not fully capture drivers perception of
  roughness, but it remains a very significant
  indicator
• Acceptable thresholds, based on IRI, can be
  identified
• Other important indicators
• Partial slab replacement
• Expansion joints
• Studded tire wear

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State Trigger Values (1998)
Criteria dependent on highway type
32
2002 IRI Statistics
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Additional Questions

• Are smoother pavements lasting longer?
• What IRI value shows improved pavement
  performance?
• What IRI value should be used as a smoothness
  specification?
• How should bonus/penalty be accessed?

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Research Report

• Shafizadeh, K., F. Mannering, and L. Pierce
  (2002). A Statistical Analysis of Factors
  Associated with Driver-Perceived Road Roughness
  on Urban Highways, Washington State
  Transportation Research Center. Research Report.
  WA-RD 583.1. June 2002. (http//depts.washington.e
  du/trac/bulkdisk/pdf/538.1.pdf)