CONTRA COSTA COUNTY
VASCO ROAD SAFETY RECOMMENDATIONS
(Updated April 8, 2004)
Background & Project Understanding
Nolte Associates, Inc. was retained by the Contra Costa County Public Works
Department to perform a conceptual roadway assessment and provide safety
recommendations for Vasco Road between the Alameda/Contra Costa County line
and Walnut Boulevard near the City of Brentwood. The study effort got
underway in mid-December 2003. The purpose of the study was to evaluate the
effectiveness, costs, and impacts of installing various median treatments,
or other applicable safety treatments, along the roadway.
This study was conducted while intersection capacity improvements were being
constructed by the County at the Vasco Road/Camino Diablo Road Intersection.
Therefore, this study did not include a comprehensive analysis at this
Data Collection & Site Visits
The County provided Nolte with digital aerial photo files, construction
As-Built Drawings, speed surveys, existing traffic volumes, and various
design reports for background material. Additionally, Nolte was provided
with collision data for the period of June 1996 through August 2003. The
source of the collision data is from the Statewide Integrated Traffic
Records System (SWITRS). Extensive coordination occurred between Nolte,
County and CHP to confirm collision data information.
Nolte reviewed all of the background material provided by the County and
visited the Vasco Road corridor on several occasions. A video recording of
the existing corridor within the Contra Costa County limits was made for
Existing features of Vasco Road reviewed by Nolte included the roadway
alignment, cross-sectional pavement widths, posted speed limits and other
regulatory signs, passing zones, and driveway access points.
Existing Roadway Section
The existing roadway consists of in general, one-12 ft. lane in each
direction with 6 ft. to 8 ft. exterior shoulders. See attached Exhibit A:
Project Map and Exhibit B: Existing Roadway Section. In the southbound
direction only, the roadway widens to two-12 ft. lanes, providing for a
truck climbing lane, just north of Brushy Creek and again, from the area
south of Brushy Creek to the Alameda County Line. The entire study area,
from Walnut Boulevard to the Alameda County Line is approximately 11 miles.
The entire length is striped with a double-yellow centerline with the
exception of two areas on either side of the intersection at Camino Diablo
Road, where a skip-yellow centerline allows for legal passing. Rural
properties abut this section of Vasco Road with driveway access to/from the
The existing roadway pavement section includes an asphalt concrete (AC)
structural section designed for traveled way traffic volumes. However, the
shoulder section was not constructed the same as the traveled way and is not
designed to carry traffic loads. If the traveled way is moved outwardly onto
the existing shoulder areas to accommodate a median treatment, the shoulder
pavement section will need to be upgraded.
All collision data from the SWITRS database for the period of June 1996
through August 2003 was plotted on a map with the alignment of Vasco Road
within Contra Costa County. The data includes all collisions resulting in at
least one fatality, all collisions resulting in at least one injury, and all
other reported collisions resulting in property damage only. A separate map
was created which only included collisions resulting in at least one
fatality and at least one injury. Additionally, a separate map was produced
to show only those collisions resulting from cross-median movement involving
vehicles in both the northbound and southbound directions. From this data,
an analysis was made on those collisions that could potentially be affected
with either a median rumble strip (also referred to as a “soft barrier”) or
concrete barrier, with a shoulder rumble strip.
In general, the collisions along Vasco Road within Contra Costa County over
the approximate seven-year period appeared to be evenly spread out between
the County line and Brentwood Boulevard with the exception of two locations.
A relatively high concentration of rear-end type of collisions had occurred
near the Vasco Road/Camino Diablo Road Intersection (71 total). The high
number of rear-end collisions appeared to have occurred due to backed-up
conditions at the traffic signal. The recent capacity improvements
constructed by the County should mitigate the backed-up condition.
Additionally, a relatively high concentration of various types of collisions
had occurred near the Brushy Creek area about five miles south of the Vasco
Road/Camino Diablo Road Intersection (23 total). This is the area where the
southbound truck climbing lane ends and transitions to a two-lane roadway
(one lane southbound and one lane northbound).
The number of collisions was also reviewed and graphed for each year of the
study period for the three main categories of Total Collisions, Injury
Collisions, and Fatal Collisions. A summary of the collision data, presented
by year, is shown on the attached Exhibits C, D, E & F. During the study
period, there were 254 Total Collisions which included 95 Injury Collisions
(number of collisions resulting in at least one injury) and 7 Fatal
Collisions (number of collisions resulting in at least one fatality).
Comparison To Statewide Average Collision Rate
A comparison of collision rates was performed between the Vasco Road
collision data and the statewide average for a similar roadway. For the five
year period from 1999 through 2003, the comparison showed that Fatal
Collisions along Vasco Road were approximately 25% of the statewide average
for collisions resulting in at least one fatality, Injury Collisions along
Vasco Road were approximately 34% of the statewide average for collisions
resulting in at least one injury, and Total Collisions along Vasco Road were
approximately 53% of the statewide average.
Development of Potential Alternatives
Nolte developed a “Long List” of potential safety improvements based on the
information that was obtained, reviewed, and analyzed. The potential
improvements included additional signage, median and shoulder minor
delineation, median and shoulder rumble strips, additional passing zones,
and median concrete barrier with pavement widening and shoulder rumble
Nolte met with County staff, the California Highway Patrol (CHP), and the
City of Brentwood staff to discuss and confirm the “Long List” of Potential
Alternatives. The collision data was then analyzed to determine the merits
of each item on the “Long List”.
A “Short List” of Potential Alternatives was developed based on the analysis
of collision data and discussions and input from the CHP, County staff, and
City of Brentwood staff.
Meetings with Stakeholders
Nolte met with corridor stakeholders to verify the assumptions and design
criteria for the “Short List” of Potential Alternatives of median and edge
treatment items. Nolte met with representatives from Caltrans, the CHP, the
East Contra Costa County Fire Protection District, and the Contra Costa
County Public Works Department.
Caltrans staff indicated, in accordance with State standards, that median
and shoulder rumble strip details can be installed without widening the
roadway, would not require a design exception, and could be implemented as
an affordable option to provide relief to cross-median and run-off roadway
collisions. See attached Exhibit G for median and shoulder rumble strip
Caltrans staff also indicated that installation of a concrete median barrier
in accordance with State standards would require roadway widening. It was
suggested to estimate the cost for two concrete median barrier options at
this preliminary level of study, to provide an understanding of the
potential range of improvement costs if this option is contemplated. One
option should include a roadway width that meets design standards for sight
distance. The other option should include a roadway width that meets an
assumed appropriate minimum width (consisting of a 5-foot median shoulder,
12-foot travel way, and 8-foot right shoulder). The difference in the two
options is the variance in width of the median shoulder that should be
provided between the barrier and adjacent travel way. See attached Exhibit H
for roadway section for each concrete barrier option.
Caltrans also provided some suggestions regarding the State Route Adoption
process. They indicated that the interested jurisdictions should make a
formal route adoption request to Caltrans to start the process, which can be
lengthy. If the process has started, Caltrans would be in a position to
formally comment on acceptability of any design criteria exceptions.
The CHP indicated that median rumble strips would not affect their current
enforcement circulation options. However, median concrete barrier would
affect their enforcement options. CHP suggested that if median concrete
barrier were installed, there needs to be a break in the barrier every one
to two miles minimum for a turnaround.
The East Contra Costa County Fire Protection District had similar comments
to those of the CHP regarding median rumble strips. Emergency access would
not be affected. Likewise, a median concrete barrier would affect their
current ability to access an emergency site. The fire department
representative agreed that, at minimum, a break in a median barrier should
be provided every one to two miles. Additionally, a minimum width of
pavement was suggested if median barrier were to be installed. The minimum
roadway width with a median barrier should consist of a 5-foot median
shoulder, 12-foot travel way, and 8-foot right shoulder (the same minimum
section suggested by Caltrans). This roadway width would provide access
around other vehicles to reach emergency sites and allow vehicles to pass
stopped equipment at emergency sites. Adequate areas on the roadway without
barrier would also need to be provided to accommodate medical helicopter
Contra Costa County Public Works staff indicated that median rumble strips
would not affect their current ability to provide roadway maintenance.
Median concrete barrier would hinder their maintenance operations making it
difficult to detour traffic around construction zones. Additionally, access
driveways relative to barrier openings would need to be discussed with the
adjacent property owners.
Conceptual Cost Estimates
Conceptual cost estimates were prepared for the “Short List” of Potential
Alternatives. The estimates included costs for construction as well as “soft
costs” such as design, environmental clearance, construction management, and
project administration. Estimates for the following four categories of
options are presented in the attached Exhibit I:
1) Options S1 thru S3 – Additional signage items;
2) Options D1 thru D3 – Additional median and shoulder minor delineation
3) Options R1 thru R4 – Median & shoulder rumble strip details, with and
without passing zones;
4) Options B1 thru B3 – Median concrete barrier with roadway widening and
shoulder rumble strip detail, with and without passing zones.
Draft Recommendations Presented To Vasco Road Advisory Task Force
Nolte provided a draft presentation covering an overview of the Safety Study
along with a recommended improvement strategy. The Draft presentation was
reviewed by CHP, County and City of Brentwood staff. Concurrence was gained
on a potentially fundable recommendation to be presented to the Vasco Road
Advisory Task Force.
On Monday, March 15, 2004, Nolte presented the study overview and
recommended potentially fundable safety improvement options to the Vasco
Road Advisory Task Force as follows:
If sufficient funds are available (estimated at $786,000), proceed as
1) Option S1 – Install “Passing Lane Ahead” signs;
2) Option S2 – Install “Do Not Pass” signs;
3) Option R1 – Install Median & Shoulder Rumble Strip Detail along entire
corridor except do not include median rumble at existing passing zones where
there is a skip-yellow centerline north and south of Camino Diablo Road.
(During design, verify appropriate width of median detail.);
4) Begin route adoption process with Caltrans;
5) Consult with Alameda County on improvement strategy;
6) Continue to monitor operations of intersection at Camino Diablo;
7) Monitor cross median incidents within skip-yellow median passing zones
north and south of Camino Diablo Road and
8) Monitor effectiveness of rumble strips on cross-median and run-off
incidents along corridor.
An Alternative Draft Recommendation was also presented to the Task Force if
sufficient funds were not available to implement the first recommendation.
The alternative recommendation would include additional roadside signage
pertaining to the passing zones, install additional delineation markers and
reflectors to the existing double-yellow centerline, and install additional
white flexible delineators along the edge of roadway at the exterior curves.
The cost for this alternative recommendation is estimated to be $160,000.
At the March 15th meeting, some members of the Task Force expressed that
they thought a concrete median barrier could be installed on Vasco Road for
a fraction of the cost prepared and presented by Nolte and therefore, did
not accept the draft recommendation to install the median and shoulder
rumble strip option. Per the conceptual cost estimates presented,
installation of a concrete barrier and recommended roadway widening for the
11-mile section of Vasco Road would cost a minimum of $34 Million. If design
standards were followed, the cost could rise as high as $82 Million. Nolte
was asked by the Task Force to obtain some historical information from
Caltrans regarding highways within the Bay Area that have a median barrier,
such as Highway 17 and Highway 37, to determine if a concrete barrier could
be installed without roadway widening. The Task Force also requested that a
Caltrans representative attend the next Task Force meeting on April 7, 2004.
Follow-up Discussions with Caltrans
Nolte and County staff met with Caltrans District 4 to discuss the
installation of potential median treatments along Vasco Road and to discuss
other roadways similar to Vasco Road where median barriers or rumble strips
If a concrete barrier was installed on Vasco Road without reconstructing the
existing shoulder to provide adequate pavement strength and widening of the
roadway, the resultant lane configuration for the entire single-lane
northbound direction and for those single-lane sections of the southbound
direction would be: no median shoulder; an 11 ft. travel lane immediately
adjacent to the concrete barrier; and either a 6 ft. or 8 ft. outside
The facilities that were identified to be similar to the Vasco Road corridor
included State Routes 12, 17, 25, 37, and 152. Upon review of the similar
facilities, the suggestion reached earlier in the Safety Study that Vasco
Road would need to be widened if a concrete barrier was installed was
validated. In no instance was a concrete barrier installed on a two-lane
(one in each direction) highway similar in width to Vasco Road without
roadway widening. In the case of Vasco Road, vehicles traveling at highway
speed in close proximity to the concrete barrier and the adverse affect on
emergency access were cited as critical concerns if the roadway was not
Caltrans confirmed that if Vasco Road was a State facility, the median and
shoulder rumble strip recommendation would be an appropriate safety
improvement without roadway widening. Vasco Road is very similar in width to
sections of SR 12. In July 2001, median rumble strips were installed on a
1-mile section of SR 12 in Napa County. In the two years following
installation of rumble strips in this section, no cross-median collisions
had been reported. Caltrans has since added median rumble strips to
additional portions of the SR 12 roadway.
Therefore, constructing a concrete median barrier along Vasco Road without
roadway widening is not recommended because it would not provide adequate
room for emergency vehicle access or for recovery of an errant vehicle.
Vasco Road Advisory Task Force Meeting April 7, 2004
At the Task Force meeting on April 7th, the County reported on the follow up
work that Nolte and the County did with Caltrans in response to the
questions raised at the March 15th Task Force meeting. Caltrans presented
information on similar highways where they have used soft barriers as well
as concrete barriers and described their statewide approach to safety on two
lane highways. Based on the additional research done after the last task
force meeting, the County again presented the recommendation to install the
median and shoulder rumble strips and to include it with their resurfacing
project this summer. In addition, the concept of using vertical delineators
in the center of Vasco Road was discussed. Caltrans is including vertical
delineators on their Highway 12 median project and have some concerns about
the long-term maintenance of the delineators. The County and Nolte have also
looked at including delineators on Vasco Road and recommend including them
in the Brushy Creek area initially and monitor how well they perform. If it
is determined that long term the vertical delineators are an effective
enhancement to the median rumble strip, the County could install them along
other sections of Vasco Road as part of their maintenance operations.
The County recommends partnering with the City of Brentwood and would like
to accept their generous offer of help in financing the recommended safety
improvements in the Vasco Corridor. This would allow the County to fully
fund the project with their resurfacing project this summer.
The County also recommends that the County and surrounding jurisdictions
continue to discuss Vasco Road to identify the future needs of the facility
in the context of an ultimate strategy for the corridor.