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From Tech Transfer Newsletter, Winter 2008
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Resources from the Transportation Library
Passing Lanes on Two-Lane Rural Roads
By Rita Evans, Reference Librarian, Institute of Transportation Studies Library
Super 2 Highways: Two-Lane Rural Highways with Passing Lanes
TTI Project Summary Report
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Design Guidelines for Passing Lanes on Two-Lane Roadways (Super 2)
Complete Report
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- Develops design guidelines that can be used to design periodic, short-term
passing lanes (called Super 2 roadways in Texas). Addresses optimum passing
lane length and spacing, shoulder width requirements, and optimum signing and
pavement marking strategies. Such passing lanes improve traffic operations
by breaking up platoons and by reducing delays caused by inadequate passing
opportunities.
Methods for Increasing Passing Opportunities on Two-Lane Roads
AASHTO, 2004, pages 250-255.
- Describes passing lanes, turnouts, shoulder driving and shoulder use. More detailed information on these techniques is available in FHWA's informational 1987 guide Low Cost Methods for Improving Traffic Operations
on Two-Lane Roads
Benefits and Design/Location Criteria for Passing Lanes
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Midwest Research Institute, Missouri DOT, 2004.
- Found that passing lanes improve percent time spent following by 10 percent
to 31 percent and accident frequency is 12 percent to 24 percent lower than
for conventional two-lane highway sections. Presents criteria to determine
where passing lanes could provide level of service and safety benefits. Looks
at five case studies from Missouri.
Incremental Improvements to Rural Two-Lane Highways
Mack-Blackwell Transportation Center, 2003.
- Focuses on three-lane alternate passing designs in Arkansas. Aspects examined
include effects of passing lane length on speed, platooning and passing, and
crash histories of transitions and passing lanes. Even though the passing lane
segment volumes were higher than the state average, crash rates were lower
than the statewide average crash rate on rural two-lane roads.
Review of the Effectiveness, Location, Design and Safety of Passing Lanes in Kansas
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Kansas State University and Kansas DOT, 1999.
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Evaluates the effectiveness of existing passing lanes in Kansas from an operational,
safety, and public perception standpoint. Provides information for locating,
planning, designing, constructing and signing passing lanes in a way that maximizes
their safety and efficiency. Addresses the geometric elements relating to passing
lanes, including lane and taper length and cross sections, and pavement marking
and signing. Available statistics show a downward trend in crashes.
Interactive Highway Safety Design Model (IHSDM)
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Federal Highway Administration, 2007.
- IHSDM checks existing or proposed two-lane rural highway designs against relevant
design policy values and estimates expected safety and operational performance.
Highway project managers, designers, traffic reviewers and engineering consulting
firms can download the 2007 release free of charge; free technical support
is also available. Includes five modules: Crash Prediction, Design Consistency,
Intersection Review, Policy Review, and Traffic Analysis.
Making Two-Lane Roads Safer
by Raymond A. Krammes and Carl Hayden
Public Roads, January/February 2003.
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- Describes the Crash Prediction and Policy Review modules of the Interactive
Highway Safety Design Model (IHSDM).
A Comparison and Evaluation of the Geometric Design Practices with
Passing Lanes, Wide-Paved Shoulders and Extra-Wide Two-lane Highways in Canada
and Germany
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International Symposium on Highway Geometric Design Practices, 1998. TRB E-Circular
003.
- Discusses operational experiences in terms of overtaking rates, speed-volume
relationships, platooning, level-of-service, accident rates and driver attitudes.
Finds that passing lanes, wide-paved shoulders and extra-wide two-lane highways
increase the level of service and decrease the accident rate compared to convential
two-lane roads.
Effective Use of Passing Lanes on Two-Lane Highways
Harwood, Hoban, Warren. Transportation Research Record 1195. 1988, pages 79-91.
- Provides guidelines for effectively locating, designing, signing, and marking
passing lanes to improve traffic operations. Presents a procedure for estimating
the operational effectiveness of passing lanes in terms of improved service.
Finds that such passing lanes are effective in reducing accidents on
two-lane highways.
Design Guide for Auxiliary Passing Lanes on Rural Two-Lane Highways
Kaub, Berg. Transportation Research Record 1195. 1988, pages 79-91.
- Identifies conditions under which the construction of an auxiliary passing
lane on two-lane rural highways is economically justified. Benefit-cost analysis
was applied to determine the average daily traffic (ADT) levels at which an
auxiliary passing lane would be economically justified as a function of section
length, percent passing zones available, cost per conflict, construction cost,
and discount rate.
Application of European 2+1 Roadway Designs
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NCHRP Research Results Digest No. 275, Transportation Research Board, April
2003, 31 pages.
- Describes how using a continuous three-lane cross section with alternating
passing lanes, known in Europe as 2+1 road design, can substantially improve
operational level of service without increasing capacity. The 2+1 is recommended
for traffic flow rates of up to 1200 veh/h in one direction. Use of 2+1 design
is appropriate for roads with a substantial percentage of heavy vehicle traffic
and it can be used in level or rolling terrain. The digest includes a summary
of European practice and recommendations for use in the U.S.
About the UC Berkeley Transportation Library
Most of the items listed in this article are available from the UC Berkeley
Transportation Library. Visit the Library homepage for
more information about the library or to request access.
- Employees of California public sector transportation agencies at
the local, state, and regional levels, including federal agencies located in
California, are eligible to request anything in the transportation library's
catalog for free. The library will even provide up to 50 pages of photocopies
of articles from journals, trade magazines, or conference reports, or scan
and e-mail the requested material.
What People Have to Say About the Transportation Library
"I have a science background, so I was searching journals for information
when I found a reference to the Harmer Davis Library. The librarian pulled
a lot of stuff and e-mailed it, plus sent copies of material that wasn't
available online. We're a rural county and we're far away. It saved
us the time and expense of my driving down and hunting for the information
myself."
Vickie Smith-Becker, Analyst, Calaveras County DPW
"I'm on a committee tasked to look five-plus years into the future
and to explore alternative fuel/rolling stock. The Town of Mammoth Lakes purchased
six new trolleys and six new cutaway buses last year. All gasoline powered.
The ski area (Mammoth Mountain) has large diesel buses—they burn five
percent bio. We've started a vehicle replacement fund, and are looking
at getting the first new piece of rolling stock around 2012. What that may
be is undetermined at this point, and as we've learned, can or will change
almost every year as we see hybrid, hydrogen, CNG, etc. come about. The information
Rita has provided me has been great."
Scott Campbell, Assistant Airport Manager, Mammoth Yosemite Airport.
For more about how the Transportation Library makes research easier for transportation
professionals in California, read this article.
Next time you're doing research, make the transportation library your
first stop. Then, send them your success story.
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