Limited right-of-way and economic realities often dictate that
public investments be concentrated toward increasing the efficiency
of and preserving the existing transportation infrastructure rather
than expanding the existing transportation infrastructure. At the
same time, it is likely that growth of metropolitan areas will
continue. A major consequence of these trends will be an increasing
inability of the existing transportation system to meet future
demand. Therefore, alternative measures must be taken to prioritize
use, such as moving more people in fewer vehicles.
Various transportation systems management (TSM) tools are
available to help achieve increased traffic efficiency on existing
transportation systems. Typical examples of TSM tools are: traffic
operations improvements at intersections, operational improvements
on freeways, improved signalization, and street system controls
(one-way streets or reversible lanes).
This guide suggests methods and designs for dedicated facilities
to encourage greater use of existing transportation systems, such
as increased use of public transit (primarily buses), carpools,
vanpools, or other ridesharing modes to help attain the above
goals. Guidance is given for planning and design of preferential
treatment for high-occupancy vehicles (HOVs). Portions of this
guide have been excerpted from the previous edition of this guide,
which this new guide replaces (3), the National
Cooperative Highway Research Program (NCHRP) HOV Systems
Manual (56), and recent research from Texas
This guide has been developed to help achieve the following
goals of HOV facilities:
• To provide travel-time savings and travel-time reliability for
• To maximize the person-moving capacity of roadway facilities
by providing improved operating level of service for HOVs, both
public and private; and
• To conserve fuel, improve air quality, and minimize
consumption of other resources needed for transportation.
HOV lanes may be provided on freeways and other roadways for the
exclusive use of buses and other HOVs so they can bypass
peak-period congestion on the general-purpose lanes. Increases in
ridesharing can be gained from this option when the time savings
are significant. The guide discusses a number of options for the
establishment of HOV accommodations.
HOV facilities are usually incorporated into existing highway
rights-of-way where width and lateral clearances may be limited.
While experience has shown that some variance in design is possible
without serious adverse effects on safety and performance, the
experiences have not been extensive enough to firmly establish new
standards specifically for these types of facilities. Therefore,
the values presented in this guide should not be regarded as
absolute, but rather as the best guidance available based on
experience to date.