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SECTION V--DESCRIPTION OF STRATEGIES
Several of the companion guides provide detailed information on speed enforcement programs
intended to reduce motor vehicle speeds. The reader is referred to these guides for more
detailed information on implementing speed enforcement. In particular, the reader is directed
to the following objectives and strategies in the respective guides:
· NCHRP Report 500, Volume 1: A Guide for Addressing Aggressive-Driving Collisions
Objective 4.1 A--Deter aggressive driving in specific populations, including those
with a history of such behavior, and at specific locations
Strategy 4.1 A1--Target enforcement
· NCHRP Report 500, Volume 5: A Guide for Addressing Unsignalized Intersection Collisions
Objective 17.1 H--Reduce operating speeds on specific intersection approaches
Strategy 17.1 H1--Provide targeted speed enforcement
· NCHRP Report 500, Volume #TBA: A Guide for Reducing Speeding-Related Crashes on High-
Speed Roadways
Objective C--Improve efficiency and effectiveness of speed enforcement efforts
Strategy C1--Use targeted conventional speed enforcement programs at locations
known to have speeding-related crashes
Objective D--Reduce Bicycle Crashes at Midblock Crossings
Strategy D1: Improve Driveway Intersections (T)
Driveway improvements are intended to modify the
EXHIBIT V-55
intersection of driveways and roadways to minimize
Unsafe Driveway Intersections may
Lengthen Conflict Areas Between Bicyclists potential conflicts between bicyclists and motor
and Motor Vehicles (Dan Burden, vehicles. The design of connections to the street network
http://www.pedbikeimages.org) has a considerable impact on bicyclist safety and access
because a significant portion of bicycle/motor vehicle
crashes (approximately 20 percent) occur when either
bicyclists or motorists ride or drive out from a driveway
without properly yielding to oncoming traffic. Every
driveway connection is a potential conflict point for
motorists, bicyclists, and pedestrians and should be
designed to minimize unsafe conflicts.
Examples of driveway intersection improvements
include:
· Tighter turn radii at driveways that slow vehicle
speeds. Curb cuts should have sufficient flare,
however, for bicyclists to complete turns into the
driveway or into the nearest lane without
"swinging wide" into the adjacent lane.
· On streets with sidewalks, the walkway should
continue at grade across the driveway to provide
for clear pedestrian movement and make it clear to
motorists and bicyclists that pedestrians have the
right-of-way.
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SECTION V--DESCRIPTION OF STRATEGIES
· Paved driveway approach aprons may be EXHIBIT V-56
better suited for intersections with Paved Driveway Aprons Help Keep Gravel
from the Bikeway
unpaved streets and driveways so that (Portland, http://www.trans.ci.portland.or.us/
gravel and debris can be contained and designreferences/bicycle/appenda1.htm)
prevented from accumulating in the
bikeways, where it can lead to unsafe
riding conditions at the driveway
intersection. Although 4.6 m (15 ft) is a
typical minimum length for the paved
apron, to better reduce transfer of gravel
and debris from the unpaved portion into
the bicycle lane, longer paved aprons
should be considered. Driveway aprons
should also not have deep "lips" or
grooves that may disrupt bicycle tires.
· Driveway right-of-ways should also be
kept cleared of foliage, signs, and other
objects that obscure visibility.
· Pavement markings may improve conditions for bicyclists at driveway intersections;
although skip-striping is typically intended to provide information to motorists about an
approaching intersection with a right-turn lane, it might also be considered as a means of
informing bicyclists that drivers might turn into the driveway.
Because every driveway intersection is a potential conflict location, reducing the number of
driveways through driveway consolidation or other measures should also be considered,
particularly for arterials and collector roads. See Strategy D2--Implement Access Management
for more discussion.
EXHIBIT V-57
Strategy Attributes for Improving Driveway Intersections (T)
Attribute Description
Technical Attributes
Targets Driveway improvements target both bicyclists and motorists. Bicyclists benefit from
safer mid-block driveway intersections, and motorists are encouraged to operate more
safely as a result of improvements.
Expected Approximately 20 percent of bicycle/motor vehicle crashes occur at driveway locations.
Effectiveness This strategy is intended to improve conditions for bicyclists at driveway locations, and
result in reduced bicyclist-involved crashes at those locations.
This strategy is expected to result in the following types of improvements:
· Provide good visibility for motorists and bicyclists accessing the roadway.
· Slow motor vehicles entering / exiting the roadway and establish pedestrian
right-of-way.
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SECTION V--DESCRIPTION OF STRATEGIES
EXHIBIT V-57 (Continued)
Strategy Attributes for Improving Driveway Intersections (T)
Attribute Description
Technical Attributes
· Reduce the chances of a bicycle-only fall or turning error when bicycles enter or
leave the roadway.
Driveway improvements also may improve conditions for pedestrians.
Keys to Success It is best to properly design and consolidate driveways at the outset. Local regulations
can require appropriate driveway design when driveways are repaired or modified, or
when new driveways are built.
Where there is a parking and/or bicycle lane, consideration should be given to
designing curb radii tighter than modern guides recommend (e.g., older cities in the
Northeast and in Europe frequently have radii of 0.6 to 1.5 m [2 to 5 ft]).
More typically, in new construction, the appropriate turning radius is about 4.6 m (15 ft)
and about 7.6 m (25 ft) for arterial streets with a substantial volume of turning buses
and/or trucks. Tighter turning radii are particularly important where streets intersect at a
skew. While the corner characterized by an acute angle may require a slightly larger
radius to accommodate the turning movements, the corner with an obtuse angle should
be kept very tight, to prevent high-speed turns.
It is important to make sure that public maintenance vehicles, school buses, and
emergency vehicles are accommodated.
Potential Difficulties Several driveway designs may cause safety and access problems for pedestrians,
including excessively wide or sloped driveways, driveways with large turning
radii, multiple adjacent driveways, driveways that are not well defined, and
driveways where motorist attention is focused on finding a gap in congested
traffic.
Local landscape ordinances and other driveway guidelines may be needed to establish
clear zones for driveway rights-of-way and maintain roadway surfaces.
Along corridors, driveway consolidation creates the need for u-turns, which can be
hazardous along roadways with high speeds or ADTs.
Large trucks and buses may ride over the curb at intersections with tight radii, creating
a danger for pedestrians who are waiting to cross.
Driveways without a level sidewalk landing may not comply with ADA pedestrian
standards. See Designing for Pedestrians with Disabilities, http://www.walkinginfo.
org/de/index.htm.
Appropriate Measures A key process measure is the number of driveways that receive improvements.
and Data
Performance measures include the number of crashes involving bicyclists at
driveways, and bicycle and motor vehicle volume data are needed to represent
exposure.
Associated Needs None identified.
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SECTION V--DESCRIPTION OF STRATEGIES
EXHIBIT V-57 (Continued)
Strategy Attributes for Improving Driveway Intersections (T)
Attribute Description
Organizational and Institutional Attributes
Organizational, Agencies may need to develop new or revised driveway design, construction, and
Institutional, and access management policies.
Policy Issues
Issues Affecting Implementation time may be affected by the amount of public involvement and
Implementation Time controversy surrounding the proposed program. This can occur during the planning,
design, and funding acquisition processes.
Costs Involved No additional costs are incurred when incorporated into original plan and construction.
Costs for retrofitting changes vary depending on existing conditions and scope of work.
For example, construction costs for reconstructing a tighter turning radius are
approximately $2,000 to $20,000 per corner, depending on site conditions (e.g.,
drainage and utilities may need to be relocated).
Training and Other Because sidewalks also cross many driveways, training on ADA requirements may
Personnel Needs be needed for anyone involved in the design, construction, or maintenance of
driveway areas.
Legislative Needs Changes to driveway requirements may require updates to local development and
construction regulations.
Other Key Attributes
None identified.
Strategy D2: Implement Access Management (T)
Managing the number, spacing, access, directional flow, and other aspects of driveway
connections protects those traveling along the corridor from conflicts with those entering
or leaving the corridor. Every driveway connection is a potential conflict point among
motorists, bicyclists, and pedestrians. Access management strategies such as providing
raised/non-traversable medians and limiting driveway access may be useful in promoting
safe bicycle travel, particularly on arterial or major collector streets, since they help reduce
the number of potential conflict points.
The principles of access management incorporate providing specialized roadways
appropriate to their intended use. The trade-off is between providing direct access and
promoting through movement. For example, the main purpose of freeways and arterials is
to move through traffic, and access should be restricted to necessary interchanges. Local
streets should generally serve all destinations, and access should not be limited. There are
exceptions, however, if management is needed to reduce non-local traffic. Access
management includes such measures as:
· limiting the number of driveways (or establishing minimum spacing between
driveways),
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SECTION V--DESCRIPTION OF STRATEGIES
· providing for right-in, right-out only movements,
· locating signals to favor through movements,
· restricting turns at certain intersections, and
· using non-traversable medians to manage left- and U-turn movements.
For more information:
· The Transportation Research Board (TRB) Committee on Access Management
identifies 10 principles or strategies of access management altogether, along
with the rationale and elements of a comprehensive program (see http://www.
accessmanagement.gov/).
· TRB also published the Access Management Manual in 2003 that provides comprehensive
descriptions of access management principles, techniques and effects, and rationale and
steps toward developing an access management program and policies.
· Oregon DOT provides extensive guidance to local communities for access management as
it relates to bicycle and pedestrian planning and facility development (see http://www.
odot.state.or.us/techserv/bikewalk/planimag/backgrnd.htm).
EXHIBIT V-58
Effective Access Management Reduces the Number of Conflict Points
(Oregon DOT, http://www.odot.state.or.us/techserv/bikewalk/planimag/backgrnd.htm)
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SECTION V--DESCRIPTION OF STRATEGIES
EXHIBIT V-59
Strategy Attributes for Implementing Access Management (T)
Attribute Description
Technical Attributes
Targets This strategy targets bicyclists who utilize multi-lane arterial or collector roadways and
left-turning motorists on those roads.
Expected By limiting and consolidating driveways, by providing raised or landscaped medians, or
Effectiveness by creating frontage roads, bicyclists and pedestrians benefit in several ways:
· The number of conflict points is reduced; this is best achieved by replacing a center-
turn lane with a raised median (left turns account for a high number of crashes with
bicyclists and pedestrians).
· Motor vehicles are redirected to intersections with appropriate control devices or
appropriate assignment of right-of-way.
· Pedestrian crossing opportunities are enhanced with an accessible raised median
and fewer conflicts with turning cars.
· Accommodating people with disabilities is easier, as the need for special treatments
at driveways is reduced.
· Improved traffic flow may reduce the need for road-widening, allowing part of the
right-of-way to be recaptured for bicyclists, pedestrians, and other users.
Benefits of this strategy include smoother vehicle flow, reduced delay, and fewer
crashes (Gluck et al., 1999; Demosthenes, 2003).
Effective access management planning can also reduce total roadway facility costs by
reducing the number of driveways and intersections. Demosthenes (2003) found that
access locations (driveways and intersections) account for more than 60 percent of
vehicular crashes in urban areas, so incorporating access management strategies can
significantly reduce urban crash rates.
Keys to Success It is difficult to retroactively reduce, consolidate or eliminate existing accesses. Policies
that properly control access should be adopted so that agencies can proactively work to
improve safety for bicyclists and motorists.
A PI&E program should be developed and implemented to educate bicyclists and
motorists of the intended purpose of the access management changes, as well as alert
them to upcoming changes in traffic patterns.
A test period may be helpful to identify and make adjustments to potential problems for
affected properties.
Potential Difficulties Limiting the number of street connections may have a negative impact on non-
motorized mobility, especially for pedestrian crossings:
· Providing for free-flow of traffic by reducing connections may result in increased
travel speeds and volumes.
· Eliminating local street crossings eliminates pedestrian crossing opportunities,
reduces pedestrian and bicycle travel choices, and may increase out-of-direction
travel.
· Reduced access to businesses may require out-of-direction travel, discouraging
walking and bicycle trips.
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SECTION V--DESCRIPTION OF STRATEGIES
EXHIBIT V-59 (Continued)
Strategy Attributes for Implementing Access Management (T)
Attribute Description
Technical Attributes
· Placing concrete barriers down the middle of the road (rather than a raised or
landscaped median) effectively prohibits pedestrian crossings.
· Improperly designed raised medians act as barriers: pedestrians should be able to
see to the other side of the street (vegetation should not decrease visibility) and
curbs should be no more than standard height.
Access management that reduces traffic conflict and traffic speeds, or reduces total
vehicle travel, is expected to result in increased traffic safety. By contrast, access
management that simply increases arterial traffic speeds can increase automobile use,
and may discourage nonmotorized transportation. Development of an access
management program should include awareness of this difference and focus on
activities that reduce traffic conflict and speed.
There may be costs associated with specific designs and changes to driveway access.
It can favor economic development in some locations over others, which imposes costs
on some businesses and property owners, and benefits others.
Appropriate Measures Performance measures include the number of crashes involving bicyclists at mid-block
and Data locations, and bicycle and motor vehicle volume data are needed to represent
exposure.
Associated Needs Access management policies need to be coordinated with land use regulations. These
policies may easily conflict with each other unless all agency stakeholders are involved.
Development of access management requires consistency so that all aspects of
motorized transportation, nonmotorized transportation, and land use
management/development support the desired outcomes.
Organizational and Institutional Attributes
Organizational, Agencies that implement access management changes should involve all potentially
Institutional, and affected parties early in the planning process. Agencies may need to develop new or
Policy Issues revised policies regarding access management, or support their governing bodies in the
development of new or revised policies. Public hearings may be required if driveway
access will be restricted or changed.
Issues Affecting It may take significant time to implement this strategy. Studies should be conducted to
Implementation Time determine whether the strategy is appropriate and to identify the most appropriate
treatment or countermeasure to address the existing environment.
Costs Involved If included in initial design and construction, access management measures might raise
or decrease costs compared to other designs. Cost of retrofit measures would depend
on the type and extent. For example, adding a raised median is estimated to cost
$15,000 to $30,000 per 30 m (100 ft). Prohibiting left turns with diverters may cost from
$15,000 to $45,000 each.
Access management activities can have a number of equity impacts. Changing vehicle
access and development patterns can harm some businesses and property owners,
while benefiting others. Property owners sometimes receive compensation for lost
access.
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