Transcript SCOD, Mahoney, Penn St, Work Zones

NCHRP Project 3-69
Design of Construction Work
Zones on High-Speed Highways
AASHTO Subcommittee on Design Meeting
June 10, 2004
Kevin M. Mahoney
Penn State University
Project Objective
Develop a comprehensive
design-decision methodology
for construction work zones on
high-speed highways.
Panel
Michael Christensen, Mn DOT (Retired) - Chair
James Kladianos, WY DOT
Russel Lenz, TX DOT
Herbert Roy, NYS DOT
Robert Schlicht, FHWA
John Smith, MS DOT
Xiaoduan Sun, U of LA
J. Richard Young, PBSJ
Kenneth Opiela, FHWA
Frank Lisle, TRB
Charles Niessner, NCHRP
Schedule
Started: August 2003
First Interim Report: March 2004
Second Interim Report: August 2005
Completion: February 2006
What we learned:
from literature
1. Crash rates: generally higher in work zones
than outside (studies vary)
2. Dominant work zone crash type: rear-end
(same dominant type as outside of work zones)
3. Dominant work zone crash location: activity
area
What we learned:
from literature
Studies of design variables/decisions effect on safety:
• Work zone length: number of crashes increases with length
• Reduction of lane width: crash rates increase
• Diversion strategy: small effect on crash rates
• Freeway entrance ramp: effect of ramps not found; accel lane
elimination or significant reduction may have negative effect
What we learned:
from survey of state DOTs
1. Current practice: substance and variety
2. Priorities for research and guidance
development under this project
State DOT Priorities
Scope of design-decision
methodology: Cross Section
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Bridge width
Clear zone *
Cross slope rollover
Horizontal clearance
Median slope
Normal cross slope
• Normal shoulder
slope
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Traveled way width *
Shoulder type
Shoulder width
Sideslope
Scope of design-decision
methodology: Horizontal Alignment
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Compound curve ratio
Radius of curve *
Superelevation
Superelevation transition
Scope of design-decision
methodology: Vertical Alignment
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Critical length of grade
Maximum grade
Minimum grade
Vertical curve
Scope of design-decision
methodology: Other
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Barrier placement *
Contractor traffic control plans *
Design speed *
Decision sight distance
Stopping sight distance *
Development Methodology: Ideal
Design variables
Expected:
Performance Model
Prevailing conditions
• Safety
• Mobility
Development Methodology: Realistic
Candidate Focused Studies
• Statistical analysis of median crossover radii and
paved roadway width
• Work zone speed profile model
• Performance of heavy trucks in work zones
• Roadside design and barrier placement guidance
• Influence of design features on driver performance
• Analyzing work zones using microsimulation
TYPICAL APPLICATION 34 (SAMPLE OUTPUT)
SPEED (MPH)
75
70
65
60
LANE A
55
LANE B
50
45
40
0
1 C 2
3
4B
5
6A
7
L8
9
10
11
12
13
14
15
16
17
DISTANCE
Sample ANN output for speed profile model
18
Directional Traffic Volume
(thousands per day)
Barrier Recommended
Barrier Study
Warranted
Barrier Study Optional
Recovery distance (feet)
Possible format for roadside barrier placement design guidance
Challenges
Data
• Median crossover, radii and paved roadway width
• Crash locations while crossover in place
Performance measures
QUESTIONS?