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Discussion With...A Traffic Engineer

We recently had an opportunity to talk with traffic engineer, Ron Müller, P.E., of Ron Müller & Associates, Traffic Engineering and Consulting Services, based out of Hopkinton, Massachusetts, to get a better understanding of his profession. Here is an excerpt from our conversation.

1. What does a traffic engineer do, generally speaking?

There are different kinds of traffic engineers. I'm on the planning/development side of things. I evaluate traffic operations for land development projects that will help improve the safety and capacity of the roads, evaluate current and projected road conditions, and develop roadway and traffic signal improvements to ensure safe and efficient traffic flow for all users of the roads, not just vehicles. Other traffic engineers, for instance those that work at the state level, may focus specifically on the design of traffic signal systems. I also prepare feasibility studies for potential development projects to identify the likely mitigation requirements and costs associated with developing a particular site as well as the strategy for permitting through the local and state approval processes. Many of my projects require MEPA (Massachusetts Environmental Policy Act) approval as well as highway access permits issued by the Massachusetts Department of Transportation (MassDOT).

2. Virtually all traffic engineers seem to rely on "AASHTO", sometimes referred to as "the Green Book". What exactly is that?

That book, officially titled A Policy on Geometric Design of Highways and Streets, published by the American Association of State Highway and Transportation Officials, provides guidance to traffic engineers about how to design streets. For example, traffic engineers who design highways on behalf of the DOT use this book all the time. Personally, I don't use it that often in my current duties, but I do rely on portions such as those related to sight distance. More frequently, I rely on the Institute of Traffic Engineers (ITE) Trip Generation manual, the Manual on Uniform Traffic Control Devices (MUTCD), and the Highway Capacity Manual (HCM). The ITE manual provides trip generation information for numerous land use types, such as residential, industrial, retail, and recreational uses, which are important when planning for a new development on a piece of property. Often times, I need to collect my own trip generation data if the proposed land use does not fit within the ITE database. The MUTCD I use predominantly for evaluation of intersections to determine if traffic signal control may be warranted and the HCM I use in evaluating the capacity of roadways and intersections.

3. Are there any interesting trends that you're currently seeing in the world of traffic engineering, either via drafting zoning or subdivision regulations and/or being advanced within the industry?

Not so much at the local level, but certainly at the state level. In Massachusetts, more so than in other New England states I work in, so much of the design and development requirements now focus on protecting the environment. Much of what you see in MEPA requirements relates to air quality and reducing greenhouse gases, and significant emphasis is placed on building design and transportation as it relates to development projects. For example, for retail shopping center projects, it is now standard for there to be mitigation efforts that include transportation demand management measures such as subsidizing transit passes for employees, offering car share or van pool programs, paid participation in transportation management organizations, on-site bike racks, adding bike lanes and sidewalks on adjacent streets, paying for a shuttle service, etc. There is certainly an emphasis on "sustainable design" for roadways and intersections, meaning I have to consider all modes of travel that will be using the roadways. This is a shift from the past where the focus was on designing for maximizing roadway capacity. For certain types of uses and/or depending on the location of these projects in relationship to existing infrastructure, accomplishing these kinds of measures can often be tricky from a traffic engineering/planning perspective.

4. What kinds of testimony do traffic engineers typically provide in litigation?

For me, most of my testimony has been given in the Land Court, Superior Court and Housing Appeals Committee (for 40B projects). I am usually asked to defend the work I performed for the project being appealed. Sometimes, though, traffic engineers are called in to critique another traffic engineer's studies or reports.

5. In a few cases previously handled by this firm, the adequacy of the "sight distance" from the various roads was hotly disputed. Can you briefly explain the two kinds of sight distance that are measured, and why two experts might disagree on this point?

There are two kinds of "sight distance" that are measured in roadway/intersection design: stopping sight distance (SSD) and intersection sight distance (ISD). In fact, up until the most recent edition of the AASHTO "Green Book", these two measurements were often not applied correctly by traffic engineers because the guidelines were not entirely specific about how to do so, and so it created some confusion. In any event, SSD is the distance needed for a vehicle traveling (at "design speed") on the roadway to safely stop to avoid a collision with a stationary object in the roadway. ISD is the distance necessary for a car pulling out of a side street or driveway to be able to see oncoming traffic and not cause that traffic to slow down unduly. Traffic engineers can sometimes disagree on these distances because the issue becomes whether to design for observed vehicle speeds-which are often over the speed limit and therefore unlawful-or whether to design for posted speed limits. Some traffic engineers prefer to overdesign to compensate for people who are breaking the law. Others, like me, make sure that oncoming traffic traveling at the observed speeds has sufficient sight distance to safely stop for cars exiting a driveway (SSD) and that cars exiting a driveway have sufficient sight distance to not cause undue delay to motorists traveling at the posted speed limit (ISD). That way, the safety of the driveway intersection is assured even for those motorists who are speeding without overdesigning (which often would require significant cutting of trees and vegetation) so that those who speed are not inconvenienced. The latest edition of the AASHTO "Green Book" is very clear on this issue.

6. Let's say a developer is planning to build a new subdivision. At what stage is it best to engage a traffic engineer?

Right up front! Typically the larger and more experienced developers are aware of this and get someone like me involved very early on. But often with the smaller projects, I am called in too late and there can be a last minute scramble to present traffic studies and proposed traffic designs to the local zoning or planning boards. This is especially true when the local zoning code may be vague as to what kind of traffic information is required, and then the developer-who has tried to compile this information himself-finds out at the first hearing that he/she has fallen short of what they need to get approval. This can be problematic for the developer because in those instances where I am called late into the project planning, often times I find that there are changes required to the site plan to make the project safe. Many times these changes can affect things like the number of lots that will be permitted (in a residential subdivision), driveway locations, on-site circulation (for commercial/industrial projects) and/or land takings required to implement mitigation measures that will be required by the project. This is why it is so important to engage a traffic engineer very early on in the process, no matter what size the project is.

Ron Müller has over 26 years of experience in the permitting of land development projects through the preparation of hundreds of Traffic Impact and Access Studies and Environmental Impact Reports involving the design of site access and off-site roadway improvements. He is registered in Massachusetts, New Hampshire, Connecticut, and Rhode Island. To learn more, please email him at ronmuller (at) verizon (dot) net, or call him at (508) 395-1576.

Written by Kristen M. Ploetz, Esq., of Green Lodestar Communications & Consulting, LLC, on behalf of Jeffrey T. Angley, P.C. Edited by Jeffrey T. Angley, Esq.

Copyright (c) 2011-2012 by Jeffrey T. Angley, P.C. All rights reserved.

Disclaimer: The information contained in this post is general in nature and for educational purposes only. No personal legal advice is being provided. If you have an actual legal issue that needs to be addressed, you should seek the advice of competent legal counsel. This post does not create an attorney-client relationship between the reader and Jeffrey T. Angley, P.C., Phillips & Angley or their attorneys.

1 Comment

Great post on traffic engineering. Bury Partners in Austin, Texas specializes in traffic, and transportation engineering. I look forward to frequenting your blog in the future.

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