Mike on Traffic

InSync - Obsolescing Traffic Counts for Signal Timing?

I do a large number of turning movement counts for re-timing traffic signals.  I'm fortunate that agencies in Minnesota believe in keeping their traffic signal equipment and operations up to date.  New technology could eliminate my role though with new systems that don't require the collection of turning movement counts.

I recently attended a webinar about the InSync traffic adaptive signal system.  Traffic adaptive computerized systems have been around for decades, but they have historically been expensive and complicated (often working better in theory than in practice).  InSync seems to have come up with a simple system that will continuously update the signal timing plans along a corridor based on the traffic volume demand.  They aren't the first to claim to do this, but they seem to be one of the first to be delivering what they promise.  I recommend sitting in for one of their sales webinars if you have anything to do with traffic signals.

The system seems inexpensive enough (+/- $25,000 per intersection for the video camera detectors and their computer that will work on top of the standard traffic signal controller).  Not much of an up charge compared with just putting in video camera detection.  I'd give their system a try if I was a traffic engineer for a city or county with all in-pavement, hardwired detectors.

They have a tough market in Minnesota though.  Most of our traffic signals have video cameras working as traditional detectors.  All of these video cameras would have to be replaced with InSync video cameras.  Now if they could use any camera detection and pass those cost savings on to the agency .....

Left Turn Arrows Explained

Protected left turns (a signal indication with red arrow, yellow arrow, and green arrow) are less efficient than protected/permitted left turns (a signal indication with red circle, yellow circle, green circle, yellow arrow, and green arrow) because motorists can choose to turn left on a green circle if there is a gap in traffic at a protected/permitted signal indication.  Basically, more left turning vehicles can get through the intersection with protected/permitted phasing versus protected phasing.

So why do we have protected left turn phasing?  Some traffic engineers think they are safer, mainly because they don't trust motorists to judge an appropriate gap in traffic.  There is some validity to this theory at intersections with high speeds or poor sight lines (safety report).  The argument doesn't hold at flat intersections with a 30 mph speed limit.

As I previously wrote about (here), Mn/DOT is working on a hybrid with a flashing left arrow that could give us the best of both worlds.

Enforcement Lights on Traffic Signals

Following is a summary of Jerry Kotzenmacher's talk at the May 13th NCITE luncheon.  He talked about Mn/DOT's experience with traffic signal enforcement lights. 

Background
Enforcement lights are added to traffic signals to aid the police in catching people who are running red lights.  Many times the police can't park in a good spot to see the red indications at a signal, the stop bar, and a vehicle simultaneously.  Typically, a police officer needs to sit off to the side of the road and radio an officer downstream of the intersection to catch the red light runner.  The indication light is put in a spot so the officer can have a good parking spot and see everything they need to pursue a red light runner.  The light turns on when the red light turns on.  These systems are starting to be used around the United States because they are safer and require less police staff.  It is hoped they will also act as a deterrent if the public knows they are being used.  Mn/DOT tested a system based on the City of Burnsville's request.

Concerns
A few concerns Jerry brought up regarding the enforcement light.

• The light is adding more of a power draw to the signal which might trick the conflict monitor.
• Will the police use them enough to justify the cost?
• Who will pay for the installation and maintenance (Mn/DOT used a blue LED light - hopefully requiring little maintenance)?
• Although a red light running ticket given using the system was contested an upheld, use of the system hasn't fully been challenged/validated in the courts.
• The installation location needs to be coordinated with the police at the intersection to make sure the light will meet their needs.

Policies
Mn/DOT will not be installing enforcement lights at every signal in their jurisdiction.  They are open to installing more enforcement lights.  Mn/DOT will review police department requests on a case by case basis. 

Accessible Pedestrian Systems

I spoke at this Wednesday's NCITE luncheon about Miovision's automated turning movement count system.  The luncheon had a technology theme.  In addition to my presentation, Sue Zarling with Mn/DOT spoke about accessible pedestrian systems and Jerry Kotzenmacher with Mn/DOT spoke about traffic signal enforcement lights.  Both talks were interesting.  I'll post about Sue's presentation here and Jerry's presentation next week.

Background
Accessible Pedestrian Systems (APS) are meant to aid the sight impaired in crossing intersections that have traffic signals at them.  The pushbuttons have arrows and braille descriptions.  They also make a slight beeping sound to help the impaired locate them.  The system has a sound detector so the beeping fluctuates based on the ambient noise levels.  The beeping stays 5 decibels louder than the ambient noise level.  When the walk indication turns on for those with normal eyesight, the APS gives verbal instructions for the crossings.  It can also give a loud warning if an emergency vehicle is detected by the signal system. 

Mn/DOT has developed a specification for APS.  They have a document online to assist agencies in prioritizing which intersections to retrofit first with APS and they have developed a spreadsheet to assist in the programming of the system.  Also, a very thorough resource for APS is located on walkinginfo.org.

Concerns
A few concerns Sue brought up regarding APS:

• It costs money.  The components alone cost about $5,700 per intersection, not including labor.
• They can be noisy.  They add 5 decibels worth of noise within six to twelve feet of the pushbutton.
• They require additional stub, pushbutton station poles which are prone to being hit by snowplows.
• Each pushbutton is uniquely programmed for its location.  If one breaks, it takes a couple of weeks to get a replacement from the manufacturer.  This is a big maintenance issue.
• You need someone who can read braille to make sure the pushbutton braille is correct.

Policies
There are conflicting judgments and legislation floating around.  In Mn/DOT's opinion, there isn't clear guidance for when APS  must be installed.  The State of Maryland and the City of San Francisco have both agreed to install APS through court settlements.  There are many open cases throughout the country, including in Minnesota, pushing for the installation of APS.  The United States Access Board has published draft guidelines that state APS systems shall be installed whenever new pushbuttons are being installed with a traffic signal. 

Mn/DOT's legal interpretation of all of this information is that each government agency needs to develop a policy for when they will and will not install APS.  They are currently drafting a Technical Memorandum to clarify their agency's position and design guidelines.  In a nutshell, Sue said they will be installing APS with all new signal systems and they are developing a ranking system based on the NCHRP guidelines for retrofitting their existing signals with APS.

Turn on Green Arrow Only, but we never switch on the green arrow?

There is an article in today’s Star & Tribune (Minnesota’s largest newspaper) about a traffic signal in my fair city.  The signal at Excelsior Boulevard and 38th Street has a “Right Turn on Green Arrow Only” sign on it for the northeast bound exclusive right turn lane.  To discourage people from using this as a cut through route, the city times the signal so the green right turn arrow won’t come up in the evenings.  It forces motorists to either make an illegal right turn or pull back onto the mainline (which could get you a ticket for careless driving) and turn at a different intersection.  This strikes me as bad design on several levels - discouraging the use of a public street, violating motorist expectation, forcing people to merge back onto a mainline, etc. 

Traffic Signal Lights - Round vs. Square

Notice anything different about the signal on the left?  Art Lebedev came up with this design which he details on his blog.  It uses square indications instead of round ones, which Art contends are easier to see and more aesthetically pleasing.  The round indications are a remnant of the first traffic signals that were created in the 1910's and 1920's.  Those original electrical signals were circles because they used light bulbs.  Now we use LEDs and could easily switch to a different shape. 

A crazier idea - why do we need three indications stacked on top of each other (answer - it used to be for the color blind)???  Now that we have LEDs, we could put different indications in one spot.  We could combine the traditional colors with traditional shapes to reinforce the message.  This would reduce the size and cost of the signal indications, which in turn would allow us to use smaller metal poles which would save significant money.  Then we run them with solar panels and wifi saving cable and wiring.....

Signal Timing Manual - Free!!!

FHWA (Federal Highway Administration) has responded to poor signal timing in the U.S. by putting together a comprehensive Signal Timing Manual.  This is the most thorough document I have seen on traffic signal timing.  It covers every aspect of traffic signals - policy/funding, signal design, timing plan design, implementation, and maintenance.  The hardest part is getting the funding to cut the technicians and engineers loose.

Need for Better Traffic Signal Timing

I had an interesting meeting yesterday with Dakota County staff (thanks Suzanne and Phong).   Based on the signal report card that came out last year (see previous post) saying our nation's traffic signal timing rates a D, they are moving forward with updating the timing at all of their signals.  The County has moved to a three year rotation, updating 50 intersections a year (they manage 150 traffic signals).   The cost/benefit of keeping our traffic signals optimized is better than ever with increased gas prices.  I hope all of our government agencies will move to an updating plan like Dakota County.  It is a straight-forward, quantifiable way for us to improve the economy and environment. 

Red Light Running Retraction?

As with most issues, automated enforcement of red light running (aka photo cop) seems to be a mixed bag.  Here is a new article from the University of South Florida claiming crashes and injuries go up at intersections with photo cop because motorists slam on their brakes and get rear-ended more often.  This finding is inconsistent with Minneapolis' experience.  Maybe the stealthy mobile unit I wrote about in my last post would get everyone to drive cautiously everywhere instead of the few intersections where they know the cameras are mounted. 

Why does a traffic signal start flashing "don't walk" at me before I can get across the street?

Drum roll please, I am about to reveal the secret of pedestrian signals....

I think most people understand the hand means stop and the "walking man" means go.  Most of the confusion comes up with the flashing hand.  Here is how it works - the flashing hand flashes at you long enough that if you stepped off the curb right when the indication went from walking man to flashing hand, you would have enough time to get across the street.  You don't need to panic if you are already crossing the street and the hand starts flashing.  Keep going. 

You aren't supposed to start crossing the street if the hand is flashing, but the reality is we time the signal generously  so most able bodied adults could get across in about half the flashing hand time.  The confusing part is the walking man is only up for 7 seconds.  This is enough time to get a crowd off of the curb to start their crossing, it is NOT enough time to get across most intersections.  Sorry, that is just the industry practice.  It would slow down the whole traffic signal operation if we increase the walking man time, which would add delay to the motorists.  As one old timer told me, we use the pedestrian indications to control the pedestrians so we can get the cars through the intersection more efficiently... no comment. 

A slight wrinkle is the "countdown timer."  It is a clock that starts when the flashing hand starts and indicates how much time is left before the hand goes solid and the traffic signal switches to yellow.  Several studies have shown these timers help pedestrians cross the street better.  It gives them more information to make their decision.   Unscientifically, I have noticed several motorists speed up when they see the timer going down to 0.

Lastly, if you push the button at the signal, it is going to give you the walking man indication pretty soon.  You don't have to hold the button down or push it 1,000 times (unless you are a kid who really likes the clicking sound the button makes).