December 20


transpPlanA month ago I wrote the 10 Things a New City Traffic Engineer Should Do.  First on my list is reviewing the city’s transportation plan.  Here are key items that should be included the plan and the new traffic engineer should think through –

  • Access Spacing Guidelines:  First on my list because you’re going to be applying these rules to the new site plans you review.  There might be a development plan sitting on your desk the first day on the job.  You also need to make sure the city guidelines dovetail with county and state guidelines.
  • Right-of-way Guidelines:  Also important for site plan review.  This defines how much public right-of-way the development should be dedicating along each street corridor.
  • Functional Classification System:  At a minimum, the streets within the city should be broken up into arterials, minor-arterials, collectors and local streets.  Typically the arterials are under the state jurisdiction, minor-arterials are largely county roads but may be a state road or two, collectors are primarily under the jurisdiction of the city but may be a county road or two, and local streets are all city.  This system map will give you a snapshot of your system. Even if you have a lot of cul-de-sacs in the local neighborhoods, hopefully you have a reasonable grid system of higher order roads to move traffic around town.   The city traffic engineer typically focuses the most attention on the intersections of minor-arterial to minor arterial, minor arterial to collector, and collector to collector.
  • Existing Daily Traffic Volumes:  Cross reference these volumes to the functional classification system map.  Hopefully you don’t have any collectors with 25,000 cars a day.  Really rough guidelines:  collectors should carry 1,000 to 15,000 cars per day, minor-arterials should care 15,000 to 35,000 cars per day and arterials should carry 35,0000+ cars per day and often more than 100,000 on urban freeways.  You probably have some issues if you have local streets carrying much more than 1,000 cars a day.   The transportation plan may be five to ten years old and the existing data in their will match the vintage of publication.  Check your most current daily volumes against both the “existing” volumes in the report and the 20 year forecasts.
  • 20 Year Traffic Forecasts:  Hopefully these forecasts are tied to the city’s land use plan, but in smaller cities all of the forecasts may just be the existing volumes multiplied be a factor (such as 1.5).  Spend time reconstructing the development that’s occurred since the forecasts were prepared.  Also think through the underlying assumptions in the forecasts.  A 25 year trendline was broken by the recession that we are climbing out of.
  • Capacity Issues:  The daily capacity volumes of different roadway cross sections (from the Highway Capacity Manual) was probably applied against the existing and 20 year forecasts to highlight corridors that are or may become congested.  Scrutinize this list based on the capacities from the current HCM (2010) if the plan used capacities from the 2000 HCM.  Also cross-reference the issues against all of the different traffic volume data sets you’ve reviewed.
  • Safety Hot Spots:  Many transportation plans don’t include crash data, but I think the better plans do.  Again, if the plan is pretty old, make sure you get current data.
  • Multi-Modal Issues:  Airports, harbors, rail and transit may be in the plan, but these areas are typically outside the control of the city and they take coordination with other government entities.  The traffic engineer should be generally aware of these modes.  Other angles of multi-modal are bicycle and pedestrian facilities as well as context sensitive design.  Hopefully the transportation plan includes maps/plans related to trails and sidewalks.  The transportation plan probably doesn’t include discussions related to how transportation systems are flexibly designed to fit the context of the area, but this concept has been around for more than a decade and could be included in the plan.  At a minimum, context sensitive design is a topic the traffic engineer should discuss with the city engineer.
  • Capital Improvement Plan (CIP):  This should be a rolling five year improvement plan that is informed by the Capacity Issues and Safety Hot Spots sections of the plan.  The CIP is a very big deal at the city.  The traffic engineer will likely have some input, but this is a plan developed by the city engineer/public works director and will be discussed/approved by the city council.  Think through the plan and try to identify issues that have been identified that are based on bad assumptions.

Please add your thoughts in the comments section…..

  • Great stuff!

    It is worth mentioning that the google search term for the debate on traffic trends is “peak car”. Being aware of such debates within the industry is definitely part of the job requirements for a city traffic engineer even if it isn’t part of the job description.

  • The list includes basic “traffic engineering” and operational issues, but not actual long-term mobility planning issues. Traditional approaches proved useless to solve even existing problems, let alone plan for future issues. Here are some suggestions

    1. Sustainable Transport Principles: Identify practical way of defining sustainability using ITE’s Sustainability task force that recently produced a report outlining emerging guidelines including triple bottom line approach to measure quantitatively the transport system’s contributions to national prosperity: link between environment, economy and social benefits.

    2. Multimodal Planning – Identify the mode priority system which is often lost in capacity “optimization” conversation. ITE’s Roadway Planning Mnaual and other new resources now provides clear directions how to select modes for types of street class.

    3. Network Planning: Start with transport (not just road) network system and connectivity principles (such as street connectivity index, active connectivity, intersection density, route directness index, and so on) to increase alternative users viability by good planning and design principles.

    4. Street Family Classification, not just Functional Classification: Adopt ITE’s new road classification system and recommended mode priority system based on land -use context. Functional road classification does not reflect land-use context or mode choice strategy, therefore, should be discarded once and for all.

    5. Identify the link between Mixed Use and Transportation: Mixing Complementary uses can reduce the demand for vehicles trips, distance travelled, parking demand, infrastructure costs and increase walking, cycling and transit uses which in turn conserve energy. Transport professionals regularly ignore health, energy and indirect cost of car uses in long-term planning. Mixed-use and TOD concepts avoid those pitfalls.

    6. Define Congestion: Despite widespread concern about congestion, there is scientific definition of congestion in current transport planning/operation practice. Congestion is often compared to cholesterol. Without cholesterol human can not survive. Too much fat also kills people. Every city needs appropriate amount of congestion to survive. After certain level of congestion, it started to degrade quality of life. Detroit is the best example. ITE and TRB developed reasonable way to measure multi-modal level-of-service systems. Use other LOS measures such as EU and UK’s Pedestrian Comfort Level to avoid HCM’s “capacity-only” approach that often ignore human comfort and reliability.

    7. Complete Street Concept: Mandatory requirements of CS concept can dramatically improve safety and avoid negative aspects of automobile uses. Identify different elements and toolbox that can be applied to redesign existing or create new streets using complete street policies, which generally improve options for sustainable users while avoiding typical “road widening” improvements that generally deteriorate quality of life for local residents.

    8. Transportation Demand Management: Eliminates the need for unnecessary trips through various innovative technologies and programs. Before solving transport problems, TDM helps to identify why demand can be contained that requires expansive capital infrastructure and operation systems.

    9. Bottom-up Perspective of Capital Investment: USA and other leading already agency developed life-cycle assessment based transport planning strategy. Traditional CIP ignores real cost of unused and unnecessary infrastructures. Mandatory requirements of certification systems (such as Green Roads Manual, SUMMA indicators, or EPA/NCHRP’s Sustainable Transportation Performance Measurement) will dramatically change capital spending strategy and focus on infrastructures that will used by local people and improve local economy instead of channelling money to fossil-fuel and big-box economy that ended up in the hand big-corporations.

  • Dewan,

    Great list! A very key takeaway from your comment is the need to integrate land use planning and transportation planning. Too often, traffic engineers are handed a development plan or land use plan and tasked with making that specific concept work.

    I love your Detroit analogy. I’ve been using them as an example for about five years, i.e. a certain level of traffic activity is a byproduct of a healthy/thriving metro area.


  • {"email":"Email address invalid","url":"Website address invalid","required":"Required field missing"}
    Mike Spack

    My mission is to help traffic engineers, transportation planners, and other transportation professionals improve our world.

    Get these blog posts sent to your email! Sign up below.