Evaluating Alternative Operations Strategies to Improve Travel Time ...

SHRP 2 L11: Final Appendices
pricing can also generate revenue, which in turn, can be used for future transportation
improvements.
5.7 Lane Treatments
Lane treatments consist of strategies that result in an added or dedicated travel lane for a
directional movement of traffic and/or a specific vehicle/user type within the current section of
roadway. The objective is often to improve the vehicle-moving capacity for peak directional
movements during congested periods of the day. Lane treatment strategies can also be applied to
increase the people-moving capacity of the facility and reduce vehicular travel demand in the case
of bus-only or high-occupancy-vehicle (HOV) lanes. Lane treatments apply to both freeway and
arterial facilities and can be implemented on a static or dynamic basis. Lane treatments represent
the most popular class of treatments for recurring bottlenecks.
Managed Lanes (HOV lanes, HOT lanes, truck only lanes, TOT lanes, HOV By-Pass Ramp).
An HOV lane is reserved for the use of carpools, vanpools, and buses—in some applications,
motorcycles can use them too. Most HOV lanes are implemented on freeway facilities adjacent to
unrestricted general purpose lanes. HOV lanes limit lane usage to multi-occupant vehicles for the
entire day or for the peak traffic hours. There are several types of HOV lanes including concurrentflow
lanes, barrier-separated lanes, contra-flow lanes, shoulder lanes, and ramp-bypass metered
lanes. The intent of HOV lanes is to increase the person-moving capacity of a corridor by offering
incentives for improvements in travel time and reliability. On average, HOV lanes carry a
maximum of between 3,400 to 4,000 persons per lane-hour. Case studies in Washington,
Minnesota, Oregon, and California document benefits in terms of improved throughput of persons
and improved reliability (3, 5, 6, 9, and 11). An inventory of existing and planned HOV facilities
is provided through the FHWA Office of Operations’ website for HOV facilities (20).
High-occupancy toll (HOT) lane facilities charge single-occupancy vehicles (SOV) for the use of a
HOV lane. Access to HOT lanes is free for transit vehicles, vanpools, and carpools. The toll
charges for SOVs varies based on the level of congestion to ensure traffic volume does not exceed
an established threshold for all vehicles in the HOV lanes such that free-flow travel conditions are
maintained. Toll collection is performed electronically using open-road tolling to allow high-speed
toll collection. Tolls are charged at fixed points along the facility (9).
Changeable Lane Assignments (Reversible, Temporary Shoulder Use, Variable). Reversible
lanes are used on arterial roadways, freeways, and bridges/tunnels to increase the capacity of
facilities that experience strong directional traffic flows, especially during peak hours. Most
reversible-lane applications on freeways are implemented by constructing a separated set of lanes
along the center of the freeway with gate controls on both ends. Changeable lane-control signs
may be used to inform drivers of the current status of the reversible lane (5, 14).
Examples of this treatment include I-15 in San Diego, the Kennedy Expressway in Chicago, I-5
and I-90 in Seattle, and the Shirley Highway in Northern Virginia. A movable barrier can be
installed along undivided facilities to physically separate opposing directions of traffic flow. A
reversible lane has also been used through downtown Stanley Park and the three-lane Lion’s Gate
Bridge in Vancouver, British Columbia (6, 14).
In Europe, temporary shoulder use is implemented to reduce congestion levels. This strategy has
been used with the automated variable speed limits in the Netherlands and Germany (8).
Variable lanes at an intersection refer to the use of variable lane-use control signs that change the
assignment of turning movements to accommodate variations in traffic flow. Variable turn lanes
change a parking or a through lane into an exclusive left- or right-turn lane during peak periods
ADDITIONAL DESCRIPTION AND QUANTITATIVE BENEFITS OF TRAVEL-TIME RELIABILITY STRATEGIES Page F-13