I listened in to the webinar ITE hosted last week regarding the traffic signal chapters in the new Highway Capacity Manual (aka HCM). Here are the slides from the presentation – Download New Signalized Intersection Methodology.
I'm excited about the changes in the new HCM. I think its a much improved tool for our use. One downside is that the methodologies are more complex and iterative, meaning you'll need software to do the calculations. But outside of college students, I don't know anyone who was doing these calcs by hand any more.
Here are some highlights from the webinar -
- Procedure added for actuated phase duration so the Level of Service is based on utilizing the actuated phasing instead of us traffic engineers guessing what the average cycle length is.
- Improved delay and queue length calculations based on research. Maybe we won't have to jump straight to micro-simulation for traffic impact studies.
- Peak Hour Factor – for whole intersection, no longer by approach or movement.
- Level of Service gradation – if volume/capacity is over 1.0 intersection is listed at F even if delay would indicate better Level of Service.
- Based on dual ring controller structure.
- HCM 2010 includes only stopped vehicles in queuing calculations where HCM 2000 included slowing vehicles.
I also attended the webinar on the Multi-Modal Urban Streets methodology a month ago, but didn't write about it at the time because it doesn't seem very applicable to me. Here are the slides from that webinar if you're interested – Download HCM – Ped – Bike – Transit Methods. My takeaway is that we won't be incorporating these methods in Traffic Impact Studies and that the calculations can be largely skewed by inputs that are subjective. I can see the methodology being useful for those doing a corridor study. I'm sure the analyses will become more refined and less subjective over time.