traffic signals

SMART Signal

| David Levinson

UM News reports on my colleague Henry Liu’s new SMART Signal Technologies startup: University of Minnesota startup to improve traffic flow on congested roads:

“Based on research from the University of Minnesota, SMART Signal Technologies, Inc., will commercialize a system to better predict and manage the flow of traffic on roads controlled by traffic lights. The system could potentially cut down on traffic congestion and help drivers save both time and fuel.
Using data from existing traffic signal equipment, the system accurately calculates queue length at signalized intersections. These data, collected in real time and archived in a database, will allow cities across the state to better mediate the flow of traffic at peak times using real time performance measures provided by the system.”

I have talked about this before. I hope it gets widely deployed, what we don’t know about travel times arterials in real-time is embarrassing.

SMART-Signal Live

| David Levinson

smartsignal

My colleague Henry Liu has been working with MnDOT the past several years on deploying the SMART-Signal system. It is live on Mn trunk highway 13, and the real-time intersection level of service, queueing, and speed data coming from the system are available online here. As the website says:

“Although measuring and archiving freeway traffic performance using commonly available loop detector data has become a norm for many transportation agencies, similar approaches for urban arterials do not exist. In practice, operational data from traffic signal systems are neither stored nor analyzed, which prevents proactive management of arterial streets. The development of the SMART-Signal (Systematic Monitoring of Arterial Road Traffic Signals) system fills in this gap. The SMART-Signal system simultaneously collects event-based high-resolution traffic data from multiple intersections and generates real-time arterial performance measures including intersection queue length and arterial travel time. The development of the system has laid the groundwork for better traffic models and control strategies and opens up entirely new opportunities for managing traffic on congested roads.
In the SMART-Signal system, a complete history of traffic signal control, including all vehicle actuation events and signal phase change events, are archived and stored. At each intersection, an industrial PC with a data acquisition card is installed inside the controller cabinet, and event data collected at each intersection are transmitted to the data server in real-time using an Ethernet connection. Using the event-based data, a set of arterial performance measures, especially intersection queue length and arterial travel time, can be estimated. SMART-Signal uses a newly developed algorithmic approach to queue length estimation based on traffic shockwave theory. Cyclic traffic shockwaves at an intersection can be reconstructed using event-based data, allowing for queue length estimation even when the queue of cars extends beyond the upstream vehicle detector. To measure travel time, SMART-Signal simulates the movements of a virtual “probe vehicle” along the arterial road. As the virtual probe moves, it can modify its own state in response to the state of traffic around it by accelerating, decelerating, or maintaining a constant speed at each time step as it encounters queues, traffic signals, and changes in traffic density. SMART-Signal can also optimize traffic signal parameters using the collected high-resolution data. Instead of relying on traditional offset optimization approaches, which are based on manually collected volume data on a typical day, SMART-Signal can account for traffic flow variations by using archived traffic signal data and the derived performance measures.
The SMART-Signal system has been field-tested on three major arterial corridors in Minnesota including six intersections on Trunk Highway 55 in Golden Valley, eleven intersections on France Avenue in Bloomington, and three intersections on Prairie Center Drive in Eden Prairie. A demonstration project is also being carried out on Orange Grove Boulevard in Pasadena, California. A large-scale implementation project currently under discussion with the Minnesota Department of Transportation will monitor 100 intersections in the Twin Cities area using the SMART-Signal system. “

Linklist: May 4, 2012

| David Levinson

Wired: Get Ready To Kickstart Project Hexapod:

“Meet Stompy. He’s a hexapod – a six-legged robot being built by a team of 15 students and three instructors at Artisan’s Asylum in Somerville, Massachusetts. And if the rendering above didn’t tip you off, Stompy holds two passengers, can walk over a car and takes up nearly two lanes of road. Needless to say, Stompy is awesome.”

Bloomberg: ‘Jetman’ Soars Over Rio: Video

“Yves ‘Jetman’ Rossy, a record-holding Swiss aerialist, flew his carbon-kevlar jetwing over Rio de Janiero on Thursday morning. During his 11-minute flight he reached a speed of 186 mph and an altitude of almost 4,000 feet.”

Amanda Erickson @ Atlantic CitiesGreening Traffic Lights By Turning Them Off :

“But how’s this for an idea to make traffic patterns greener (and, proponents say, safer): stop using traffic lights altogether. The so-called “naked streets” movement has gained traction across Europe, even in major cities like London.”

[Note to jargon-heads, naked streets = shared space].

Standing There Like Idiots

| David Levinson

There are many useless traffic signals. (Some are also useful).
The most useless traffic signal I see everyday (multiple times) is at the intersection of Beacon St. and Harvard Avenue. Not only is there little traffic for the traffic light, so a stop sign (or better a yield sign, roundabout, or shared space) would do, the pedestrian signal has Beg buttons. I just saw someone who looked a lot like Eric Kaler (who is obviously not an idiot) waiting and needlessly obeying the law while pushing the pedestrian signal actuator multiple times to call for a walk signal, which eventually came. If no one pushes the actuator, you actually don’t get a walk signal, so it is working, just pointless.
Why do we have these signals, on a university campus of all places, making pedestrians (who probably are equal in number to cars at this intersection) stand there like idiots while cars can drive through, and even make a “right turn on red”?

Linklist: February 21, 2012

| David Levinson

KurzweilAI: Traffic intersections of the future will control autonomous vehicles : “Intersections of the future won’t need stop lights or stop signs. They’ll look like a somewhat chaotic flow of driverless, autonomous cars slipping past one another as they are managed by a virtual traffic controller, says computer scientist Peter Stone, a professor of computer science at The University of Texas at Austin.” [Interesting, but I disbelieve this is the likely technology path, there are 1 million signalized intersections and lord knows how many stop signs in the US, autonomous vehicles will develop protocols with each other before most jurisdictions fix their pathetically antiquated traffic signal controllers.]

Joe Verdoorn @ Newgeography Unintended Consequences of the Neo-Traditional City Planning Model: “This tactical criteria of the Neo-traditional model, however, can create unintended negative consequences. The criteria to which I refer includes:

  • grid street patterns
  • connectivity to adjacent neighborhoods
  • mixed, non-residential land uses
  • alley access/rear loaded house

The inflexible application of these tactical criteria enhances opportunities for criminal activities to occur.”

Via Martin Engel: CALIFORNIA HIGH SPEED RAIL on Vimeo: “a short, fun jaunt through history comparing the Ca. High Speed Train budget to other big ticket national projects.”

Bradley Heard @ GGW Ride The Tide of light rail, Virginia Beach – Greater Greater Washington: “Dubbed “The Tide,” South Hampton Roads’ light rail system made its debut in Norfolk on August 19, 2011. The initial $338 million segment, operated by the regional transit agency, Hampton Roads Transit (HRT), is 7.4-miles, has 11 stops, and is currently located only within Norfolk’s city limits.
…
Initial weekday ridership during the first year was projected to be only 2,900. However, the 6-month data shows that those early projections have been blown away. About 4,642 people ride The Tide during an average weekday. An even higher number—4,850—use the system on Saturdays, with 2,099 usually riding on Sundays.” [Dumbing Success Down: If they forecast Zero Riders, it would have been Infinitely more successful]

Google Killed Map Traffic Estimates Because It Just Didn’t Work

| David Levinson

From Gizmodo: Google Killed Map Traffic Estimates Because It Just Didn’t Work

If you’re wondering how road traffic’s gonna slow you today, don’t turn to Google Maps anymore—the site’s killed its estimates. Not because it wasn’t popular. It turns out those road calculations didn’t exactly correlate to, you know, reality.
The Atlantic describes the discovery of perturbed Maps users, who complained to Google when they noticed the change. Its answer?

[W]e have decided that our information systems behind this feature were not as good as they could be. Therefore, we have taken this offline and are currently working to come up with a better, more accurate solution. We are always working to bring you the best Google Maps experience with updates like these!”

Translation: traffic didn’t work. And as the Atlantic’s Nicholas Jackson asks, how could Google be sucking down so much locational data from Android drivers and be botching it to the point that they pulled it down entirely? [The Atlantic]”

A big defeat for the biggest information provider. But using in-vehicle GPS on mobile phones as a probe is coming, and will eventually get it right (approximately, if lagged). The problem of course is that traffic is dynamic, and even a 5 minute lag will be quite off if there is an incident or something non-steady state. However as a signal of whether things are normal, it probably works.
See:

Information provision is probably best for what an individual will not know from routine behavior—random incidents and unfamiliar territory. The qualitative conclusion that incidents and the unexpected are where the greatest gains from traveler information are to be found reinforces the results from our simulations. Those models show that a low level of probes can provide useful information by rapidly detecting incidents, whereas a much greater number is needed to provide any gains from recurring congestion.

Power-grid experiment could confuse clocks

| David Levinson

From MSNBC: Power-grid experiment could confuse clocks

A yearlong experiment with America’s electric grid could mess up traffic lights, security systems and some computers — and make plug-in clocks and appliances like programmable coffeemakers run up to 20 minutes fast.
“A lot of people are going to have things break and they’re not going to know why,” said Demetrios Matsakis, head of the time service department at the U.S. Naval Observatory, one of two official timekeeping agencies in the federal government.
Since 1930, electric clocks have kept time based on the rate of the electrical current that powers them. If the current slips off its usual rate, clocks run a little fast or slow. Power companies now take steps to correct it and keep the frequency of the current — and the time — as precise as possible.
The group that oversees the U.S. power grid is proposing an experiment that would allow more frequency variation than it does now without corrections, according to a company presentation obtained by The Associated Press.

I have long thought there should be a time stamp on the electric grid power signal, something quite small, but that could be read as embedded information (some highly non-random sequence) from modulation of the phase or frequency of the AC cycle. Other means for synchronizing clocks rely on other networks (internet, GPS, radio, etc.), some old discussion here. This is similar to the idea of powerline modems, but not nearly as sophisticated (i.e. I just want a time signal).

Seeing Red: Why L.A. Needs to Keep its Traffic Light Cameras

| David Levinson

Eric Morris has a nice post on the Freakonomics blog: Seeing Red: Why L.A. Needs to Keep its Traffic Light Cameras

Policemen on the street, on the other hand, are vastly more invasive and potentially unjust because they are surveiling you when you are not breaking the law, have the ability to bust you on more severe charges emanating from a traffic stop (e.g. if you have drugs in the car), have fallible judgment about whether you were in the intersection, and have the ability to enforce the law selectively (e.g. racial profiling). If privacy is your concern it would actually be far better to have RLCs, but ban police from the streets. If you concede that it is kosher to have policemen on patrol I see little basis for arguing against RLCs, which are actually considerably more benign.
A major problem for RLCs is common to many public policies: those who are punished know who they are, but the beneficiaries do not. Also, it is hard to point to the benefits of something not happening. People who get tickets from RLCs are often bitter, and can turn into vocal enemies of the program. However, there are hundreds of people walking around today whose lives were saved by an RLC but will never know that they cheated death thanks to a camera. Consider that you might be one of them. Or if you really do hate RLCs, I’d suggest you fight back and teach those money-grubbing bureaucrats a lesson… by stopping at each and every red light.

Alas they are unconstitutional in Minnesota.