Civil Engineering Reference
In-Depth Information
17.3.1.1 High Occupancy Vehicles Lanes (HOV)
HOV lanes reserved for the exclusive use of multi occupancy vehicles, including
transit vehicles. The objective of HOV lanes is to reduce single occupant vehicles
use. This is achieved where the trip times of HOV users is competitive with the trip
time of single occupant vehicles. In fact, improved travel time is often cited as the
major reason for using an HOV lane in surveys of HOV lane users [
18
]. By
controlling the minimum vehicle occupancy, HOV demand can be limited to
demand-to-capacity (D/C) ratios that can sustain desirable speeds.
HOV lanes are desirable where the general purpose freeway lanes are congested
(operating at Service Level
“
E
”
); the lanes are long enough to save users at least
10 min, and there is suf
cient HOV demand in the corridor. However, they should
not
be provided by taking lanes from the general purpose lanes in the peak hours of travel.
Urban areas in the US that have HOV systems of at least 50 miles include: Los
Angeles, Seattle, Denver, Salt Lake City, and Washington DC
Types of HOV Lanes
As shown in Fig.
17.12
, HOV lanes can be created in a number of ways [
18
]:
Two-Way Concurrent Flow
—
This is the most common application. Additional
lanes are provided adjacent to the freeway median in each direction of travel.
They are normally separated by painted lines from the general purpose lanes and
sometime include additional space for vehicles entering and leaving the lane.
Contra-
this typically entails use of the inside lane of a freeway (located in
the opposite direction of peak
fl
ow
—
fl
flow) by high occupancy vehicles traveling in the
peak direction of
flow. The lane is typically separated from the off-peak
direction by plastic pylons or movable concrete barriers.
fl
Contra-
ow lanes are used in New York City on some expressways leading to
Manhattan from Queens and Brooklyn.
fl
Physically Segregated Median Lanes
A two-way roadway located within the
freeway median physically separated from the general purpose freeway lanes.
The rebuilt Katy Freeway in Houston has a segregated median HOV roadway.
—
Queue Bypass
HOV lanes provided to bypass recurring congestion points can
reduce travel times and increase travel time reliability of high occupancy vehicles.
—
17.3.1.2 High Occupancy Toll (HOT) Lanes
These lanes are typically available without charge to HOVs, but they charge a toll to
other vehicles at a price set to vary with traf
c demand tomaintain free-
fl
owing traf
c.
cient demand, while adjacent general use
lanes are congested, HOV lanes can be converted to High Occupancy Toll (HOT)
Lanes.
Where HOV lanes do not generate suf
