Mike on Traffic

Snow on LED Signal Indications - Low Tech Solution

My last post discussed snow covering LED lights.  Its a story that doesn't seem to want to go away. 

I came across a low tech solution sold by McCain (a large traffic signal supplier whose products are widely used in Minnesota).  Their Scoop Tunnel Visor has a beveled opening that provides air circulation around the LED lights which reduces snow build up.  They cost about $20 each (which isn't much of an upcharge if they are being put on new signals instead of the standard visor). 

The Colorado DOT has been using the scoop visor and seems to think they work.  According to CDOT spokeswoman Mindy Crane - "They've helped immensely in terms of keeping the snow off the traffic lights.  It's not high-tech and it's very economical."

Snow on Traffic Signals Lights

Most of you have probably heard about snow sticking to LED traffic signal lights, blocking the view and causing crashes.  The Associated Press put together an article on the topic this week.  It even quotes a few people from Minnesota.

The problem discussed in the article is slushy snow that falls in a windy storm can fly onto and then stick to the signal lights.  Old fashioned light bulbs were warm and would melt away the snow.  Most traffic signals have upgraded to using LED lights which allow the snow to stay because they aren't warm.  

There was a big push for LEDs about ten years ago because of the economic benefits (LEDs last longer and use less power - they're about three times more economical than incandescent lightbulbs).  I was a member of the local traffic signal committee and we discussed LED lights at length, including their inability to melt snow.  Another big issue was whether or not we need a $2000 battery backup system at every signal to keep the lights working when the power goes out (see MnDOT's dark signal report). Our conclusion after going through crash data was that there are few crashes caused by a traffic signal light that can't be seen.  Most people are more attentive in snowy or power outage situations and come to a voluntary stop when they are uncertain.

I would prefer to see the media focus on inattentive driving.  I think this is a much bigger safety issue (although its harder to get good photos for a news story).  Here are the crash risk results from a 2006 study by the Virginia Tech Transportation Institute (these results don't fully address the impacts of texting):

• Driving drowsy increases an individual’s near-crash or crash risk by four to six times.
• Engaging in secondary tasks that require multiple steps or eye glances away from the forward roadway increases risk by two to three times.
• Certain behaviors increased the risk of involvement in a near-crash or crash. Reaching for a moving objects increased risk nine times, looking at an external object 3.7 times,reading 3.4 times, applying makeup 3 times, and dialing a hand-held device 2.8 times.
• Talking or listening to a hand-held device increased risk by 1.3 times, but this result wasnot statistically different than normal driving.
• Looking away from the forward roadway for long glances at inopportune moments increase crash risk by two times that of an alert driver.

New Type of Red Light for Traffic Signals

Damjan Stankovic of relogik has come up with an innovative red light indication called the Eko.  It is a type of countdown red light for traffic signals (we already have numerical countdown indications for pedestrian lights).  The bars circling the light go dark as the wait at the red light gets shorter. 

The Eko could have two benefits -

(1) Less Stress - Drivers would see that they are getting closer to a green light.  It's the same concept used by computers with the spinning hour glass when you are opening a file or program.

(2) Environmentally Friendly - There are some folks out there who turn off their engine at a red light to save gas.  The Eko would let those people know when to turn their car back on.  Maybe this would encourage more people to use this gas saving/pollution reducing technique.

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.