Sedona City Talk: Andy Dickey, Public Works Director

Sedona AZ (May 22, 2019) – Who are those yellow vested people in Uptown and on SR 179 and what are they doing?  I’d like to clear up just who these folks are and some mis-conceptions about what they’re doing.

The city’s public works department began managing the Traffic Control Assistants (TCA) program in 2017.  At that time, the goal was to develop a program to help with the worst traffic in the busiest seasons. Challenges filling the part time positions meant limited success in fiscal year 2017 (July 2016 to June 2017) because we were only able to implement the program 46% of the high congestion days (travel time greater than 30 minutes). 

Not only are these positions difficult to fill, due to being part time, but the job requires standing for long periods of time, often in the hot sun, and often while being yelled at by those that don’t appreciate or understand what the TCA’s are doing.  Although we find the TCA’s to be very effective in helping to reduce the impact of pedestrian interference with traffic flow, they are often not appreciated by those stuck in traffic backups. The pedestrians also often make disparaging remarks, as they don’t appreciate being asked to wait. 

Some believe the TCA program is aimed at interrupting traffic to prioritize pedestrians.  It is in fact the opposite. The program focuses on making pedestrians wait and queue, so vehicles can flow through.  This is similar to the way a traffic signal operates, with stopping and queueing in a timing sequence intended maximize efficiency.

Some ask, why not just place a traffic signal at crosswalks, rather than the TCA’s?  The answer is found in uptown at mid-block, where we utilize the TCA’s to control pedestrian traffic, even though we have a traffic signal.  Without the TCA’s, pedestrians often cross the highway against the stop indication of the signal, or vehicles stop at the crosswalk against a green light, due to a pedestrian being at the edge of the crosswalk.  These interruptions may not seem like a big deal to the casual observer. However, it’s the cumulation of these types of interruptions that eventually leads to congestion. In the traffic engineering field we refer to these interruptions as “friction.”  By implementing the TCA program, we reduce friction on vehicle traffic, which helps reduce congestion.

How effective has this program been? In February 2017, the city began collecting travel time data for the congested segments of highway in the city.  We looked at weekends between February and November in 2017 and 2018 and found that TCAs reduced a typical 33 minute congestion event by 9 minutes,

Each year the TCA program has continued to improve.  In fiscal year 2019, we expect to have maintained traffic control operations 89% of the days experiencing high congestion, increased from 49% in fiscal year 2018.  This correlates to 103 days in Uptown SR 89A and 131 days on SR 179.The successful implementation of the program has come from improving staff recruitment and retention.  

In the future the city will look to expand this program where we can to help reduce congestion.  This may include placing traffic control operations in new locations, expanding hours of operation, or assisting the program with new technology.  City staff continue to research intelligent transportation system technologies in an effort to discover new control measures to help reduce congestion.

How will the new Sedona in Motion (SIM) projects affect the TCA program?  Both the SIM and TCA programs address congestion. Some examples include planned Uptown Roadway Improvements project (SIM-01) and a Pedestrian Crossing at Tlaquepaque on SR 179 (SIM-04).  While these projects will also help relieve friction on vehicle traffic, we believe TCA’s will still be necessary to fully control pedestrian movements at crosswalks. The SIM-01 project also reduces friction caused by u-turning, and left turning vehicles.  The SIM-04 project provides an alternate pedestrian route, allowing on street crosswalks to be closed during high congestion events.

When passing by our TCA’s please remember to thank them for the effort they put into a difficult job that many don’t realize is making a significant and positive impact on congestion in the Sedona community.