Evaluating Alternative Operations Strategies to Improve Travel Time ...

SHRP 2 L11: Final Appendices
with protecting the workers and the work zone, not necessarily with minimizing traffic impacts.
Incentives on the part of agencies and contractors are generally small, and there is little real-time
monitoring of performance. Work zones on freeways are estimated to account for nearly 25% of
non-recurring delay (1, 16).
ITS applications in work zones include the temporary implementation of traffic management or
incident management technologies. These temporary systems can be stand-alone or be
supplemental to existing systems during construction. Other applications control speed limit
displays or notify travelers of changes in lane configurations, travel times, and delays through the
work zones. Systems for work-zone incident management can also be used to rapidly detect
incidents and determine the appropriate degree of response needed, thereby limiting the amount
and duration of additional capacity reductions. ITS solutions for work-zone management include
components such as smart work zones, traveler information/portable DMS, dynamic lane-merge
systems, variable speed-limit systems, and portable traffic management systems including
surveillance and detection, and safety service patrols. ITS may also be used to manage traffic
along detour routes during full road closures as a result of reconstruction projects (5, 9).
Examples of work zone management applications in the United States include Colorado DOTs
traffic incident management program for several long-term construction projects (the T-REX
project in Denver and the COSMIX project in Colorado Springs), and the North Carolina DOTs
real-time work-zone information system on I-95 north of Fayetteville in 2002 (14). Also, Caltrans
has a software package for work-zone management designed to address traffic impacts. .
Infrastructure Improvements and Demand Optimization
5.1 Geometric Design Treatments
Bottleneck Removal (Weaving, Alignment). The improvement or elimination of weaving
sections can be accomplished through changes in striping and/or lane assignments, the use of
medians to physically separate traffic flows, reconfiguring ramps to add/restrict movements, and
realigning ramps to increase weaving distance or eliminate a weaving conflict. Weaving sections
reduce vehicle speed, capacity, and reliability in addition to contributing to safety deficiencies.
Improving weaving sections may increase roadway capacity to a degree similar to basic freeway
sections or ramp merge/diverge area.
Horizontal and vertical alignment modifications primarily apply to older facilities (arterials and
freeways) that were designed and built before modern day roadway design standards were
established. Sharp horizontal or vertical curves affect the speed profile of vehicles and,
anecdotally, can lead to sudden breaking that increases the probability for a breakdown (6).
Geometric Improvements (Interchange, Ramp, Intersections). Geometric improvements refer
to spot reconstruction or minor geometric widening performed within the existing paved area.
They are considered low to moderate cost improvements and less significant than a major capital
improvement project. Spot geometric design treatments, such as auxiliary lanes, flyovers,
improved weaving section designs, interchange modifications, and minor alignment changes, can
be part of an Active traffic management package of measures. Every major metropolitan area of
the United States has examples of spot geometric design treatments used to alleviate freeway
bottlenecks (6, 14).
Flyovers apply to interchange ramps and major through or turn movements at arterial intersections.
They are generally considered a spot treatment to address a high-volume movement as opposed to
full reconstruction or lane widening of a facility.
ADDITIONAL DESCRIPTION AND QUANTITATIVE BENEFITS OF TRAVEL-TIME RELIABILITY STRATEGIES Page F-7