MARIN COUNTY ON-CALL SERVICES
​Four Corners Intersection Final Alternative.    Jan 2019, Constructed 2021 based on PRISM Engineering Design

Engineering design and drawing by Grant Johnson, TE © 2019

COMMENTARY ON IMPROVEMENTS BY GRANT JOHNSON, TE :

  • This intersection will undergo a huge safety and design improvement. Traffic will slow significantly to 15 mph.  Traffic operations will improve. Bikes can safely navigate, etc.
  • The deflection angle for the NB approach matches deflection angle used in single lane approach or dual lane approach modern roundabouts and as published in the MUTCD. This angle has a traffic calming influence. It will slow traffic to safe speeds, such as in the range of 15 mph - 20 mph. The radius of the approach entry curve is 100 feet.  This also applies for the southbound movement, but the curve is on the exit.
  • Striped islands are being used, with thick wide lines to clearly delineate the area that should not be used.  
  • The centerline of the SB approach has been modified to expand to a short loop area about 3 feet wide and then tapering back to the center, providing some better definition for the vehicle pathways.  All vehicle pathways have been checked, are tangential to the lane curves, centerline striping and edgeline striping at intersection approaches clearly directs vehicles in a smooth and logical path.  It has been designed for smooth movement of vehicles, through 12 foot wide lanes.
  • The turns in the intersection according to the proposed striping shown, have been tested with the Caltrans HDM truck turning templates for a large bus and pass the test.
  • The Muir Woods EB approach has been significantly moved forward, as well as the WB approach.  Stop signs have been relocated. It is possible to see previous markings through the slightly translucent black overlay layer.
  • The Panoramic Highway NB approach has also been moved forward significantly, and the length of the left turn pocket has increased from and existing 115’ to 140’ with the proposed striping.  The intersection as a whole is much tighter together.
  • The warning signs proposed will guide drivers that a 15 mph advisory curve is at hand.  
  • The centerline striping for the NB and SB approaches has been extended through the intersection according to the MUTCD standards on Fig. 3A-112(CA).  This also serves as a kind of refuge for the left turns out from NB Panoramic Highway.  
  • The NB approach and the SB approach have both been modified with Speed Reduction Markings for the through lanes. MUTCD Fig. 3B-28 details the size and spacing of the markings, and this plan has been implemented accordingly.  These markings should be sufficient to alert drivers that a slowing in speed is expected, and with the warning sign clearly in place at the end of the markings, drivers should have slowed to 15-20 mph, according to the curve and deflection implemented. It is possible to also install rumble strip traffic calming devices, but not necessary if these other devices are installed.

​Google Street View UPDATES to Four Corners Intersection Final Alternative (Photos Mar 2021).   
Designed Jan 2019, Constructed 2021 based on PRISM Engineering Design

This was the "Before Improvement" traffic operations safety problem at this intersection.

video © 2019 PRISM Engineering

Transportation Planning SAMPLES by PRISM Engineering  

Traffic Impact Studies, Traffic Demand Models, Multimodal Corridor Studies, Transit Studies, Roundabouts

​EMERGENCY RESPONSE!  Fire Engine Response Study.    Feb 2019, Fairfield, CA

​photo/video © 2019 PRISM Engineering
PRISM Engineering conducted a comprehensive emergency fire engine response time study to determine if adequate emergency response times are in place according to established standards (NFPA 1710). Out of nine nearby fire stations, 3 were within the standards, and only one needed to be. A complete report with tables and graphics was prepared to document all findings, and detailed times on all travel paths. Google Maps App was also researched to make comparisons of actual drive times in the field, and to verify.    The purpose of the study was to find out through engineering methods (research, measurements, analysis, and summary) what fire engine response times from various fire stations proximate to the project site would be, by physically measuring and video recording actual driving times from each station to the site, adjusting times for red lights along the way, considering the effects of traffic congestion, and taking into consideration what happens when a fire engine deploys traffic signal pre-emption to bypass a red light at an intersection, etc. In addition, “big data” from Google Maps was also used, a publicly available data set that documents the ranges of time that drivers experienced along a certain path while using the Google Maps App.  A detailed info-graphic and summary matrix and report were prepared to show optimum pathways and times from nine different nearby fire stations to the project site, during the “worst case” pm peak hour time period.

ROUNDABOUT in 2018/2019-- In El Dorado County:  Dorado Oaks Residential Development in Diamond Springs UPDATE: Traffic Impact Study and Operations Analysis and
Modern Roundabout Mitigation of State Highway (2016-2019)
This study includes a comprehensive Traffic Impact Study, a Traffic Operations Analysis and Micro-simulation model(s) for the Missouri Flat Road corridor from Plaza Drive to SR 49 Pleasant Valley Road (2 miles).   Multiple scenarios were analyzed for Year 2017, 2025, and 2035 conditions with and without the project.  Detailed analyses were performed using calibrated micro-simulation SimTraffic models, and mitigation measures explored along with the future Diamond Springs Parkway bypass in the Travel Demand Model network.

FIG 1: Existing Condition lacking capacity, intersections too close and narrow to mitigate.

FIG 2: Proposed Roundabout solves capacity, speed, geometry, and LOS for Project Expansion

Project is 400 Residential Dwelling Units

Coming up with solutions for this study was particularly challenging:  
1) There is a new bypass that will change traffic patterns in the future.
2) There is a narrow historical road which serves as State Highway 49 which can't be expanded or signalized easily.  So a roundabout solution was sought to preserve the historical buildings, prevent widening, and keep speeds reasonably slow and safe.
​3) Access issues abound where driveways are numerous and sidewalks are not installed.
4) Bike lanes are missing because of narrow roads and right of way issues
5) New development is required to find more connectivity between neighborhoods, and minimize impacts by encouraging walking, biking, and use of transit where possible. 

Year 2019 Trip Generation and Traffic Patterns Study: understanding traffic characteristics, trip generation
At PRISM Engineering, we build a solid baseline of existing conditions to establish traffic patterns, then build on that and analyze the future...

​photo/video © 2019 PRISM Engineering





Contracted with the UNITED STATES, DEPARTMENT of JUSTICE:  

EXPERT WITNESS in Traffic Engineering (2018)
Grant Johnson, TE (registered Traffic Engineer)

Working with the United States Attorney's Office in the Department of Justice, Mr. Johnson was retained to perform Expert Witness Traffic Engineering review of an accident case, including field review, examination of roadway traffic control devices and compliance with relevant Federal documents such as MUTCD*, deposition, court testimony.


​*MUTCD=Manual of Uniform Traffic Control Devices, FHWA
​photo/video © 2019 PRISM Engineering



3rd and 4th Quarter 2017 Highlights
​PRISM ENGINEERING

-ON-CALL SERVICES-

In the City of Vacaville:  The Farm at Alamo Creek TIA (2017-2018)
                                            750 unit planned Specific Plan Development

CUBE model. Synchro. HCS Freeway. SimTraffic. Intersection Design.

The Farm at Alamo Creek TIA.pdf
File Size: 54898 kb
File Type: pdf
Download File

Report Samples. Trip Generation. CUBE 6.4 Traffic Demand Model. Excel Database. Synchro HCM Analysis. Mitigations

-ON-CALL SERVICES-

In Marin County:  Four Corners Intersection Improvements (2017)
                                 Panoramic Highway at Muir Woods Road

Observations. Video. Sight Distance. Synchro. Intersection Design.

FOUR CORNERS work_order_report.pdf
File Size: 38729 kb
File Type: pdf
Download File
​photos © 2019 PRISM Engineering

SIGHT DISTANCE and SPEED STUDIES

AERIAL VIEWS and NEW INTERSECTION DESIGN


​1st and 2nd Quarter 2017 Highlights
​PRISM ENGINEERING

Report Files

In Redwood City:  Rocketship Charter School Study, PRISM Peer Review:  Parking, Safety, and Circulation (2017)

In this study PRISM Engineering examined on-street parking saturation, and how the proposed Rocketship Charter School would impact circulation and parking in the area. 

A peer review of the traffic study was done.  In addition, traffic conditions were analyzed and a letter report prepared.  It was found that Charter Street would be severely impacted during arrival of school children, should this school be built in this location, on account of lack of storage and parking.

In El Dorado County:  El Mirage Commercial and Residential Development at US 50 and El Dorado Road.
​Traffic Impact Study (2017-2018)
This study includes a Traffic Impact Study, a Traffic Operations Analysis and Micro-simulation model(s) for the El Dorado Road corridor from Echo Lane to Runnymeade Drive realigned.  Coordinated signal system.    Multiple scenarios were analyzed for Year 2017, 2025, and 2035 conditions with and without the project.  Detailed analyses were performed using calibrated micro-simulation SimTraffic models, and mitigation measures explored along with the future Diamond Springs Parkway bypass in the Travel Demand Model network.

In El Dorado County:  Stonehenge Springs Residential Development in Diamond Springs Traffic Impact Study and Operations Analysis (2016/17)

This study includes a comprehensive Traffic Impact Study, a Traffic Operations Analysis and Micro-simulation model(s) for the Missouri Flat Road corridor from Plaza Drive to SR 49 Pleasant Valley Road (2 miles).  Multiple scenarios were analyzed for Year 2017, 2025, and 2035 conditions with and without the project.  Detailed analyses were performed using calibrated micro-simulation SimTraffic models, and mitigation measures explored along with the future Diamond Springs Parkway bypass in the Travel Demand Model network.

In Marin County:  Alta Way Peer Review (2017)

Examining Traffic Conditions (level of service, speeds, sight distance, left turn pocket lengths, trip generation, etc) for new residential development on Alta Lane extension.  Peer Review of pre-existing traffic studies.  Working as sub-consultant to Sicular Environmental Consulting and Natural Lands Management under contract with Marin County.

In City of Vallejo:  Caliber Charter School Traffic Impact Study and Follow-up Intersection Mitigation Alternatives Development and Analyses (2016/17)

Worked with City of Vallejo Staff to develop workable circulation and student arrival solutions to minimize queues and impacts to local streets and intersections.  Developed custom traffic control plan for neighborhood.  Developed trip generation scenarios based on TDM plan for staggered start times of classes at Charter School.  Ran analysis scenarios for Year 2016, 2026, and 2035 using traffic model output from Solano Transit Authority travel demand model.  Collected new traffic for wide region of intersections.

In Marin County:  Expert Witness Review of MUTCD and Highway Design Manual Compliance (2017)

In City of Manteca:  Roundabout Installation, Expert Witness Review (2017)

In Marin County:  On-Call Traffic Engineering Services Contract with Department of Public Works (2017)

In City of Lincoln:  On-Call Traffic Engineering Services Contract (2016/17)

In City of San Rafael:  Safe Routes to School Field Review and Analysis of Multi-modal Traffic and Ped conditions.  
​Teamed as sub to Parisi Engineering (2016/17)
Extensive Capacity Analysis for High School Alternatives.  Reviewing parking lot situations for high school expansion.  Extensive review of on-street parking impacts existing and future expansions.  Pedestrian and vehicle flow analyses for surrounding neighborhoods.  Develop solutions to reduce traffic impacts, reduce impacts to local neighborhoods, and  Improve safety for children walking or biking to school.  

Conducted video surveys of existing traffic patterns and pedestrian travel patterns. Through video observations above and beyond the traffic count data, it was possible to observe critical traffic conflicts with both vehicles and pedestrians. It was possible to track origin and destination movements, giving a big picture understanding of transportation modes and movements. Examined condition of all installed Traffic Control Devices and recommended new installations where safety was an issue.  Developed large scale graphics to provide big picture understanding.
INFOGRAPHICS developed by Grant Johnson, TE to communicate big picture situations, team communications, report graphics


​3rd and 4th Quarter 2016 Highlights
​PRISM ENGINEERING

In the City of Vallejo:  Charter School Traffic Study.        Trip Generation Research.  Synchro 9 Analysis.  Microsimulation.  Mitigation.  Report.
PRISM Engineering was hired by the City to complete a comprehensive traffic study examining multiple scenarios for school traffic mitigations, including:
  • staggered arrival times,
  • on-site storage of arriving traffic,
  • controlled access patterns and parental cooperation with arrival and departure patterns,
  • raised medians and controlled traffic patterns designed specifically for the school on local streets, and
  • attendance at meetings to explain our methodology. 
Result?  Passage of Project.
traffic_study_new_revised_vallejo_charter_school_3.pdf
File Size: 5178 kb
File Type: pdf
Download File

Other Studies Underway or Recently Completed
  • PRISM Engineering working with Government Traffic Engineers for On-Call services in Bay Area Marin County, City of Vacaville and Lincoln
  • PRISM Engineering teamed with Parisi Transportation Consulting in late 2016 on a traffic study for the San Rafael High School expansion.
  • PRISM is teamed in Marin County, CA with Sicular Environmental Consulting for a 2017 CEQA Services study pertaining to residential development. PRISM is the traffic consultant part of the team.
  • PRISM completed Expert Witness traffic engineering reviews during 2016-2018 in the Cities of Pittsburg, San Rafael, Manteca, and Richmond, CA
    • site inspection, video analysis, accident review, design review, etc
  • PRISM teamed with REY Engineers and secured on-call traffic engineering services in the City of Lincoln, CA
  • PRISM Engineering is completing a major 2017 traffic impact study and traffic operations analysis in El Dorado County, CA
  • PRISM Engineering is in progress on completing new 2017 traffic analyses and studies in Vallejo, CA
  • PRISM Engineering is starting up work on major 2017 traffic analysis in El Dorado County, CA which includes microsimulation
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