If you have ever had a question or needed some information about the Highway Capacity Manual (HCM 2010) or the Highway Capacity Software (HCS 2010), all you have to do is ask us.  McTrans has been involved with the Transportation Research Board (TRB) Highway Capacity and Quality of Service (HCQS) committee for about thirty years and has followed every detail of the HCM development to be able to implement the procedures in the HCS.

With 15-20,000 end users of the HCS, we have heard and been able to answer most questions immediately.  If any research is required to find the answer, we do that thoroughly – putting that question on the immediate answer list going forward.  Over thirty years, we have compiled quite a resource to deal with almost any situation right away.

We have also been presenting training courses for over twenty five years to detail every procedure in the HCM to equip users to apply those methods using the HCS over all of this time.  Even though we are software developers, our courses focus mostly on the HCM procedures to explain the inner workings of each methodology and the intricate details included in results – necessary to generate accurate analyses using the HCS.

Don’t spend countless of hours digging though the HCM or scratching your head trying to figure out how to analyze a particular intersection, highway or freeway. We can likely get you going in minutes by email instead of you taking hours to find the answer.

There may even be questions you don’t know to ask – many aspects of these procedures appear to be largely misunderstood.  For example:

• Did you know that queue spillover is not modeled by the signalized intersection methodology? For instance, if the queue in a left-turn lane exceeds the storage and spills out into the adjacent thru lane, the reduction in the thru-lane capacity is not modeled.  That means if the queue storage ratio exceeds 1.0, the results are likely invalid for that approach and must be modeled using alternative tools.

• Did you know that oversaturated conditions must be modeled using a multiple-period analysis in the signalized intersection procedures? That is the only way to incorporate the unmet demand from one period as the initial queue for the subsequent period for the computation of d₃ delay – which can change the overall delay results from seconds to several minutes.

• Did you know that the capacity models for roundabouts will change dramatically with the publication of the HCM 6^th Edition and its implementation in HCS7? Especially for single-lane roundabouts, the new equations will generally result in much higher capacity values to generate much lower delays for improved level of service.

• Did you know that the freeway facilities procedure must be used to model oversaturated conditions? Whenever a basic, weaving, merge or diverge segment analysis results in LOS F, a freeway facilities analysis is necessary to quantify the interaction of multiple segments over multiple time periods to generate delay and queue results.

Let us know if anything ever comes up or you just want to confirm what you are doing (or have always done) is compatible with the HCM.  We stand ready to help code the data, explain results, resolve a problem or just review your analysis – just ask me!

Thanks,

William M. Sampson, P.E.
McTrans Center Director
bsampson@ufl.edu
352-294-3095