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CONTRA COSTA COUNTY
VASCO ROAD SAFETY RECOMMENDATIONS
SUMMARY REPORT
(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 intersection.

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 office reference.

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 facility.

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.

Collision Data

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 strips.

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 detail.

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 landing zones.

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 items;
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 follows:

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.);

Additionally:

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 were installed.

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 shoulder.

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 widened.

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.

Recommendation

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.
 

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