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Signal Performance Metrics

This is part 2 of 4 in our blog series on Traffic Insights. This post covers Signal Performance Metrics. Stay tuned for more!

In part one of this series, we covered the evolution of data-driven traffic operations. We looked at the obstacles many cities face in implementing modern systems. And we didn’t forget to cover the benefits:

1. Better payback from infrastructure investments and 2. Better served citizens.

Both are driven mainly by the traffic insights available from Spectrum.

These insights fall into three main categories: Signal Performance Metrics (the subject of this blog post), Arterial Performance Metrics, and Maintenance and Infrastructure (which we will cover in future posts).

Design, Tune and Troubleshoot with SPMs

Signal Performance Metrics (SPMs) are a set of measurements and visualizations that help traffic teams design, tune, and troubleshoot traffic intersections. They are part of Miovision Spectrum, a turnkey solution for remote traffic signal optimization.

Spectrum provides the entire range of solutions needed to collect, monitor, and understand traffic signals. This includes a managed cellular connection and tools for signal monitoring, video streaming, maintenance alerts, and traffic data insights.

Spectrum’s analytical tools and reports generate actionable information from the raw traffic intersection data. SPMs provide intersection-level reporting of key metrics like:

  • Vehicle volumes
  • Wait times
  • Problem detection

Do These Questions Ring True?

If you recognize the questions below, your team is a good candidate to test these solutions.

SPMs help traffic agencies answer the most basic questions like:

  • Are my traffic signals working?
  • What kind of traffic volumes are we seeing?

But also deeper-level questions like:

  • Do we have an appropriate allocation of green time between movements?
  • Are we meeting our goals on vehicle wait times at rush hour?

How Are SPMs Generated?

Spectrum captures event data from the traffic controller, detectors, and other cabinet devices. This data includes signal state, pre-emption, and detector actuations. This is generated from stop-bar and upstream count detectors and pedestrian call button actuations.

Spectrum’s cabinet hardware is able to generate this data even from cabinets housing older traffic controllers. These typically do not produce high resolution reporting. The raw data is securely stored in Spectrum’s cloud where analysis is performed to extract meaningful information and actionable insights.

screen-shot-2016-11-14-at-9-45-34-am

What are the Infrastructure Requirements for Signal Performance Measures?

Although Spectrum Traffic Insights can be useful in an intersection with no detection, the set of available analytics expands with additional detector infrastructure.

With no detectors, Spectrum SPMs include:

  • Red/Green Allocation: The proportion of green time allocated to each approach and movement.
  • Pre-emption Summary: Reports of pre-emption events, durations, and triggers, including railroad crossings or emergency vehicle pre-empts.

With stop-bar detection data, Spectrum SPMs include:

  • Red and Green Occupancy Ratio: Gauges the demand for the various phases based on the ratio of time that vehicles are present in the associated movements. This allows for tuning of split times between phases.
  • Purdue Split Failure: Industry-standard metric that charts the frequency of split failure occurrences, an incident where green signal time fails to meet the vehicle volume demand.
  • Simple Delay: Simplified approach delay measures the time between detector activation during red singals and movement service at start of green signals. Simple delay approximates the overall delay experienced by intersection users.

With advanced upstream detection, Spectrum SPMs include:

  • Arrival Volumes: Counts of total vehicle traffic through an intersection from each approach.
  • Arrivals-on-Red vs. Arrival-on-Green: Counts of total vehicle volume arriving during red or green, giving a rough sign of progression quality for the given movement.
  • Purdue Coordination Diagram: A graphical representation of individual vehicle arrivals relative to cycle time (red, yellow and green), highlighting arrival characteristics, and platoon progression quality.
  • Average Delay: The length of time vehicles are delayed at a congested intersection.

What do SPM Dashboards and Reports Look Like?

We’ve included three screen grabs for dashboards that are generated by Spectrum.

The UX is designed to 1. Be as simple as possible for a big data set and 2. Show performance patterns over time.

Check these out!

Approach Volume: chart showing the volumes for the chosen day compared to the previous 12-week weekday average and variability bands.

approach-volume-pg11

Arrivals on Red/Green over a 12-week period showing the average volume of traffic arriving at the intersection during the red or green phases at different times of the day.

arrivals-on-red-pg11

Occupancy Ratio chart showing the stop bar occupancy ratio during red, green, and the first 5 seconds of subsequent red (ROR5) for each cycle of a selected movement.

occupancy-ratio-pg12-1

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Feeling informed? Part three of this blog series will appear in two weeks. It will cover Miovision Traffic Insights for Arterial Performance Metrics.

How Seattle Transformed a Dangerous Intersection Through Data

There’s an intersection in Seattle located in the Madison Park lakeside neighborhood where a ½ mile hill leads right into a populated business district. There sits Seattle’s busiest Starbucks location and a Wells Fargo Bank. This arterial connection is both the neighborhood’s busiest intersection for pedestrians and a city-designated school crossing location. Due to the rampant speeding and sight-line problems with this location, people walking often have difficulty crossing the street without trepidation.

Busy intersection at East Madison Street and McGilvra Boulevard East in Seattle

It took a serious collision between a cyclist and a pedestrian to force the city to try and fix the problems with the intersection. That’s where Bob Edmiston, his team from Seattle Neighborhood Greenways, and volunteers from Tableau saw an opportunity to make difference.

Their success would all depend on the data.

The Long and Winding Road to Funding

The plan for Seattle Neighborhood Greenways was to conceptualize and implement a safer intersection strategy for pedestrians. First, the team secured a $90,000 grant through Madison Park Community Council to enable the Seattle Department of Transportation (SDOT) to redesign the intersection.

However, to secure the addition $390,000 necessary to implement the changes, they would need to prove that the redesigned intersection would actually solve a problem. On top of that, there is a competitive pitching process for allocating grants in Seattle divided by district. Edmiston and his team were competing for the top spot against 15 other grant projects from the area. After initially failing to convince the decision makers of the value of the project by using an emotional appeal, a more persuasive approach was desperately needed.

If the team didn’t win the grant right now, their project would be dead.

Answering the Call with Data

Seattle Neighborhood Greenways sensed that they needed quantifiable proof of the improved safety of their solution. To collect the evidence necessary for a persuasive argument, Edmiston built a traffic counter that could record gaps in traffic with millisecond precision and conducted a gap analysis of the intersection. Seattle Neighborhood Greenways volunteer Troy Heerwagen worked with Edmiston to visualize the data using Tableau Public for ease of understanding.

Edmiston made some key observations:

  • During the critical 15-minute period before the morning school bell, there were only two opportunities with gaps long enough to walk across the street.
  • Crossing distance reductions provided by the curb extensions would reduce the crossing time enough to triple the number of safe crossing opportunities for pedestrians during the critical 30 minutes before the morning school bell, without requiring any changes to driver behavior or roadway function.
Intersection Video Data

Bob’s Visualized Data

After presenting the new data and logic to the East District Neighborhood Council, the people responsible for funding decisions were convinced that the project would, in fact, produce the safety outcomes it promised. They reversed their earlier decision to not fund the project and chose to make it their top priority for 2017 funding.

Don’t Underestimate the Data

Edmiston reminds us to not underestimate the data, when he says,

“data matters, counts matter, gap analysis matters. We would have been dead in the water without it. But it’s about being able to show data in a way people can understand and relate to. That’s an equally important part of the problem.”

If it weren’t for the data collected, Seattle’s busiest intersection would still be dangerous for pedestrians. More so, it was the way team presented the data through visualization that made it digestible and accessible to everyone.

Miovision is passionate about enabling other change-minded individuals to use data to justify their road safety solutions.

Want to learn more how we can help you leverage meaningful data? Contact us today.

Utah DOT Celebrates 100th Anniversary of the Traffic Signal

A replica of the first electric traffic signal unveiled by UDOT Executive Director, John Njord.

On October 4, the Utah Department of Transportation (UDOT) celebrated the 100th anniversary of the modern, electric traffic signal. It was invented by Lester Wire, a Salt Lake City police officer, back in 1912. He was looking for a way to control busy intersections as congestion was growing and could potentially be a safety issue.

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Traffic Studies: Overview for Starting the Fall Count Season

Now that the summer holidays are over, we’re getting back into the swing of things and starting to ramp up our fall count season. This season is usually hectic for transportation professionals who are executing transportation projects which include executing or requesting traffic data collection.

To provide some information into traffic data collection, the next two week’s blogs will be focusing on reviewing a few study types, their applications and challenges.It’ll provide some insight into how engineers are utilizing each study type and perhaps it will apply to your objectives.

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Miovision Introduces Traffic Data On Demand

Miovision is a leading provider of traffic data collection technology, specifically through our Scout video collection units (VCU). The Scout provides traffic engineers with the ability to easily collect traffic data by deploying these portable, non-intrusive units to record traffic movements within an intersection which are processed using our proprietary video analytics software.

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Top 5 Reasons to Automate Your Spring Counts

Spring is officially upon us and transportation professionals are in the midst of kicking off the traffic count season. Last week’s blog, Top 3 Traffic Data Projects to Start Off Your Spring Count Season, focused on maximizing your traffic data collection efforts amongst three transportation projects.

This week, we’ll focus on why many transportation professionals are now automating their traffic studies. The start of a new year provides a great time to step up your traffic data collection efforts and leave the manual counters in the dust.

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The State of America’s Transportation Network

The American transportation network is in dire need of highway maintenance and reconstruction. Valued at $1.75 trillion, it has endured years of wear and tear, increased traffic, inconsistent maintenance and varying weather conditions. All of these variables, along with higher construction costs and reduced government funding have contributed to only half of the nation’s roads being in good condition.

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Roundabout Safety Improvements

Roundabouts are becoming more common in urban areas and with good reason. They are known to improve traffic flow and safety in comparison to other forms of intersection control such as traffic signals. However, problems can arise from using roundabouts since traffic signals and signs have been the standard for so long. Understanding how to best optimize roundabouts and prevent accidents will ensure that traffic flow is being optimized.

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Traffic Impact Analysis for Growing Cities

I’m not sure what it’s like in your city, but from the Miovision offices, Kitchener-Waterloo (KW) and surrounding areas are aggressively expanding. With each new subdivision built, there are new plazas, office buildings, and parkades popping up. In certain areas of the city, the landscape (or what used to be landscape) has completely transformed.

One area in particular has completely changed – the Ira Needles area. This previously empty area was just an open field next to Trussler and Erbsville Road. In 2009, it was transformed into the largest commercial centre in the KW area that spans across 88.5 acres. To accommodate the anticipated influx of traffic, additional roads were built as well as 6 roundabouts were utilized rather than lights to facilitate traffic flow.

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Top 5 Difficult Conditions for Manual Counting

Manual traffic counting is time consuming. It can take even longer and reduce accuracy in certain weather conditions. Whenever there is poor weather, there is a higher chance for lower quality data as the onsite counter just wants to get the study done and go back to the office.

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