PRISM Engineering Expert Witness Services

SAFETY. Above all else, Safety is the first priority with Grant Johnson, Traffic Engineer, who is regularly examining the safety of transportation systems and traffic control devices... to determine if the installations are safe, normal, and customary. Was common sense used? He can help you on your next case to determine if a traffic control installation is / was standard according to AASHTO, MUTCD, State and Local Standard Plans, etc., or if there was an error made which contributed to an accident.

An extension of Traffic Engineering, Expert Witness research and testimony are about intimate knowledge of the regulations and details, documentation, and precedent.

Grant P. Johnson, TE is a registered Traffic Engineer in the State of California, the only state in the union with this special distinction. Now a requirement of many government jurisdictions to qualify traffic studies, the Traffic Engineer is being asked to sign documents as an authority on the subject of all things pertaining to traffic and regulation. In Expert Witness testimony and research, the title of Traffic Engineer enhances credibility.

Mr. Johnson is currently working on several Expert Witness cases in California including multiple Bay Area Cities, as well as Southern California cities and counties.

EXPERT WITNESS CASE HIGHLIGHT:
Sleuthing the Flawed Design and Traffic Control of a New State Highway, SR 85 in Utah

A new beautiful and scenic highway is built to serve numerous new communities, paralleling Interstate 15 in Utah's Salt Lake Valley. Two huge corporations collaborate to design the north and south half of a segment of this highway. The problem? Accidents started happening in the middle where these two designs came together.
A huge mound of dirt was hauled in as shown on the design plans, to create a smooth elevation far above a new apartment complex (to alleviate noise), but in the process a dilemma zone was created just before what was later to become a fully signalized intersection with Rosecrest Road. The dilemma zone was the combination of a terrible and unnecessary vertical curve sight distance constraint (could not see intersection just hundreds of feet away from intersection, a stopping sight distance issue with high speeds), and a horizontal curve right after the crest, to the right, creating a confusing picture to a driver approaching this signal, far off to the right, unclear and a driver is faces with a high speed dilemma. It was here that northbound SR 85 traffic had not only this last minute vertical curve after steady two mile rise going 55-65 mph, but also just after this crest the highway curves "suddenly" to the right, and traffic signals suddenly appear right in front of the driver. Coming up the grade, the traffic signals are barely visible, set low over the horizon down off to the right, seemingly not relevant to the SR 85 northbound traffic. It is at this point that many drivers are faced with a dilemma, especially if they are only now realizing that the signal is red and it applies to them, and there is a car in the intersection coming off of the side street Rose Crest Road, brakes are slammed, numerous skid marks imprinted on the pavement for those who avoided an accident, and no skid marks for the ones who were completely caught unaware and did not realize what was happening, kept going and apparently oblivious that they were running a red light and about to have a high speed and fatal collision. Several of these similar accidents happen, highway traffic hits side street traffic (who has the right of way) and fatalities happen. And a mitigation eventually happened: A huge overhead flashing yellow beacon was installed to warn drivers of a red signal ahead (see AUG 2022 google street view evidence of installation, years after the accident and case was settled). A Traffic Engineer would have known that this was a dangerous situation and an accident waiting to happen. Indeed they did happen. The flashing beacon should have been installed in the first place, as it was at so many other signalized intersections along SR 85, but this intersection was passed over due to cost constraints by UDOT, even though this signal had the most safety challenges for drivers.

The Mountain View highway was originally set with a 45 mph speed limit, and then in 2013 UDOT changed it to 55 mph based on an engineering Speed Study showing the prevailing speeds (85th percentile) of 57 mph.

Once the speeds were set higher, the challenge to stop a vehicle at a red light becomes even more difficult. The nine different skid marks shown on the pavement in red are for the NB approach (north is to the right on Figure 3). All skids are within a range of 570 feet back of intersection stop bar (next to crosswalk) to 250 feet back of the stop bar.

Three skids start in the #1 lane (left-most), and six start in the #2 lane. Skids start at or near the BIKE SYMBOL where the bike lane dash starts (just about 200 feet before the crest, or 500
feet before the stop bar), where previously hidden striping (hid by vertical curve) suddenly becomes visible to the driver.
It is not a coincidence that skid marks are happening at this point where a change in striping direction takes place, and where it suddenly becomes visible. This dilemma situation is the combination of a horizontal curve (road alignment change taking place after the crest) and a vertical curve where the adequacy of sight distance for drivers heading towards the intersection is marginalized, and intersection perception is significantly marginalized. The numerous skid marks indicate a pattern of driver reactions to the situation at this location, or to the signal itself being suddenly recognized and when the signal light is red.

PRISM Engineering reviewed and studied the original design plan sheet sets for the actual construction of the SR 85 highway, and discovered that thousands of cubic years of earth fill were brought in to elevate the highway, but it was elevated too much and then one can see by looking at the topography of the final result, there is an unnecessary dip in elevation back down to Rose Crest Road. This was even more apparent in the profile drawings which showed the original earth elevations, which were about 20 feet higher than the original ground. This lift in elevation for SR 85 brought its height unnecessarily high, and then lowered to Rose Crest Road, creating the unnecessary vertical curve. It was a man made vertical curve and should not have been designed or approved considering the traffic engineering and safety challenges it posed. In the end, fatalities happened at this intersection, which was not signalized at first. Ultimately, it became a four legged signalized intersection, but having a vertical and horizontal combined curve on SR 85 that obscured a driver's view of the intersection and traffic operations.

PRISM Engineering reviews field conditions using high definition aerial photos, correlates this to plans, and examines to scale, locations of skid marks, striping, and pole installations, etc. in relation to the intersection.
photo/video © 2019 PRISM Engineering

Aerial view of the dilemma zone area on SR 85 looking north at Rose Crest Road shortly after the first fatal accident. During the trial of this case, another similar fatality (high speed broadside hit) happened at this same location, sealing its fate as a dangerous intersection as is. The newly installed flashing yellow beacon will help as per MUTCD guidelines, but the vertical and horizontal sight distance constraints still remain.
photo/video © 2019 PRISM Engineering

PROJECT HIGHLIGHT: Traffic Engineering & Design

In Marin County: Four Corners Intersection: Panoramic Highway

Working with the Marin County's Attorney's Office, 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*.

*MUTCD=Manual of Uniform Traffic Control Devices, FHWA

Contracted with the UNITED STATES, DEPARTMENT of JUSTICE:

EXPERT WITNESS in Traffic Engineering (2018-2019)
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*.

*MUTCD=Manual of Uniform Traffic Control Devices, FHWA

Grant Johnson, TE, has extensive experience designing traffic signal plans including equipment placement, conduit and electrical systems, as well as all signing and striping relating to intersection control.
He can review existing signal plans and determine if the signal meets standard plans, and whether signing and striping was properly installed. He can also determine adequacy of advance detector systems, flashing beacons, etc., and especially as these various traffic control devices comply with your state's MUTCD and other Highway Design standards of safe stopping sight distance, etc.

SIGNAL DESIGN and REVIEW of INSTALLATION

Example of Expert Witness work: Detailed examination of intersection and signal installations from aerials, plan sheets, and site inspection, by PRISM Engineering

INTERSECTION EXAMINATION of TRAFFIC CONTROL

PRISM Engineering understands the standards relating to proper and improper traffic control device installations, including signals, poles, signing and striping, as they relate to the guidance in the MUTCD*, the AASHTO Green Book, FHWA**, Highway Design Manuals, and Engineering Judgment.
*Manual of Uniform Traffic Control Devices
**Federal Highway Administration
photo/video © 2019 PRISM Engineering

EXAMPLE OF SIGNAL DESIGN WORK: El Dorado Hills Green Valley Road Corridor Signal and Interconnect Design by PRISM Engineering

In this On-Call Services work order, PRISM Engineering worked directly with El Dorado County Department of Transportation Design Staff to create the signal design layers in the extensive AutoCAD design file with XREF overlays. Grant Johnson, TE was project manager of this work effort and designed the conduit runs, pole and detector locations, signal phasing and diagrams, signing and striping.

PRISM Engineering has completed numerous signal design projects over the years, and integrated these plans with development applications where street and intersection improvements are required as a part of a traffic impact analysis. PRISM has the ability to take things from the planning stage of forecasting traffic, to the analysis stage of determining intersection and road segment improvements, and warranting of traffic signals for a new installation, or the modification of an existing signal expanded to include more lanes, etc. We have also designed inter-connected signal installations where traffic volumes between intersections are coordinated with offset signal cycle timings, and analyzed using SynchroPro and SimTraffic microsimulation.

http://www.marincounty.org/depts/bs/meeting-archive

In this case he spoke before the Marin County Board of Supervisors on a hotly contested and controversial topic and discussed the traffic operations study results, and how information was shared with Caltrans, etc. Remaining low-key, stick to the facts mingled with common sense, and avoid contention.

Grant Johnson, TE has extensive experience in making public presentations on technical topics, and in making them understandable and credible.

Link to local newspaper story on this BOS decision and process:
story: http://www.marinij.com/article/NO/20160413/NEWS/160419920

PUBLIC PRESENTATIONS, sample from San Francisco Bay Area

TRAIN CROSSINGS

Train crossings can be considered with two different perspectives: A perfect and fully funded world where all signals and gates with flashing lights work flawlessly, and were perfectly designed (giving DRIVERS, BIKES and PEDS an expectation of safety), or in a less perfect but real world where rail road crossings exist but only have basic signals and gates, or even just a simple RR XING Warning Sign to warn the drivers they are crossing a track, and there are no gates and lights (typical of some rural conditions). Standards, safety goals and installation methods vary from jurisdiction to jurisdiction, situation to situation, and there is not a one-size-fits-all solution. There are manuals and standards that address different situations.

DRIVERS EXPECTATIONS at RR XING

Many accidents can be traced to a scenario where a driver was met with an unexpected situation, or where they were suddenly surprised and did not know how to respond in time to avoid an accident. In the video below, the highly unlikely scenario where a Chicago rail road gate timer was so badly off, that the gates lowered completely AFTER the train already had passed through at high speed. Three cars narrowly missed getting hit by the train.

PEDESTRIAN EXPECTATIONS at RR XING

Imagine a signal installation or train crossing where the drivers think they are safe to cross or move forward, but for malfunction of a gate or signal, people's lives are put at risk.

Fortunately in this case all three drivers of different cars survived missing the high speed train, a highly likely fatal situation.

What responsibility to pedestrians have when crossing a railroad track? Should they wear headphones with loud volume so that they can not HEAR a train? What about the blind, who can't see but can hear the train? Are flashing signals, chirping audio sounds, the lowering gates, the ringing bells, and the sound of a roaring train approaching sufficient to protect the blind pedestrian, let alone the other pedestrians, riders of bikes, and drivers of vehicles who should be aware while using the transportation facilities? How much protection is too much, and how does this relate to "expectations?"

PRISM Engineering conducts Expert Witness consulting work in the following areas:

Examination of Traffic Control Installations; Recommendations for Safety Enhancement, Intersection Design and Layout, Signal Design / Timings and Operations, Crosswalk Locations and Warnings, Railroad Pre-emption, Speed Limits, Pavement Delineation, School Areas and Traffic Control, Curve Warning Signage and Roadway Conditions, etc.

Using the guidance and regulation contained in the AASHTO, MUTCD, and State and Local Standard Plans and manuals, Grant Johnson, TE can review any traffic control device installation including signs, striping, pavement markings, sight distance with grades and curves and obstructions, etc., to determine compliance with accepted standards and engineering judgment. Examples follow:

Collision History Diagrams and Analysis.

PRISM Engineering identifies Crash Patterns through research and an analysis of the crash data on record for specific locations. To do this we create a collision diagram (see image to right), make a collision summary, conduct field reviews, etc. to obtain all relevant information possible.
PRISM creates a summary table of the crashes that occurred during the study period, and shows pavement conditions, crash type, lighting conditions, number of injuries or fatalities, and any other relevant information, such as driver-related facts (i.e., age, gender, restraint use). This makes it very useful to identify crash patterns.

Guard Rails and Embankments, Curves, Bridges. Median Barriers, etc.

Guardrail installations can be complex.

The decision on whether to install one depends on a number of factors of safety and engineering including,

slope and grade,
presence of fixed objects,
bridges and rails,
curvature,
speed of travel,
cost, etc.

Sight Distance Studies and Analysis

Stopping sight distance: the distance needed for drivers to see an object on the roadway ahead and bring their vehicles to safe stop in time before colliding with the object. We analyze these parameters based on speeds traveled and specific geometry of the road and any visual obstacles in place.

PRISM Engineering understands AASHTO, FHWA, and MUTCD standards for traffic safety and roadway standards, including standard plans compatible signal design and installation.

Construction Area Traffic Control Examination, Temporary Traffic Control, Long Term Traffic Control

Source: MUTCD

PRISM Engineering also has expertise in:

PRISM Engineering can review the adequacy of traffic control plans used by a City or County during construction projects. Traffic control planning requires forethought. Provisions may be incorporated into the project bid documents that enable contractors to develop alternate traffic control plans, which may be used only if the responsible agency finds they are as good as those provided in the plans/specifications. For maintenance and minor utility projects that do not require bidding, forethought must be given to selecting the best traffic control before occupying the temporary traffic control zone. Also, coordination must be made between projects to ensure that duplicate signing is not used and to ensure compatibility of traffic control between adjacent projects. (MUTCD, OSHA, CALTRANS, etc)

PRISM Engineering is familiar with the detailed MUTCD manual, which defines the standards used by road managers nationwide to install and maintain traffic control devices on all public streets, highways, bikeways, and private roads open to public travel. The MUTCD is published by the Federal Highway Administration (FHWA) under 23 Code of Federal Regulations (CFR), Part 655, Subpart F. States must adopt the National MUTCD as their legal State standard for traffic control devices.

Pavement Conditions. Access Management. Parking Lot Layout. Street Lighting. Light Rail.

Depositions, Court Testimony

Expert Witness rate sheet available upon formal request ...

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Expert Witness SERVICES