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Featured Insights

Inefficient Traffic Signals Cause Unneeded Delays & Congestion

Almost every driver has experienced the annoyance of getting stopped by a red light at a deserted intersection. Or just the opposite, traffic so congested that you’ve had to wait through several light cycles to make a left turn. At times, it feels like the traffic signals are conspiring against us. Why can’t the traffic lights adjust to actual roadway conditions?

With standard traffic signals, retiming events might only occur every few years, and the process is reliant on time-consuming, manually collected data over a several day period. Even then, typical time-of-day signal timing plans don’t accommodate for variable and unpredictable traffic patterns. To make matters worse, when poorly timed, traffic signals (particularly along busy corridors) significantly contribute to traffic congestion, excess fuel consumption, and frustrated drivers.

Automated Traffic Signal Performance Measures (ATSPM) & Adaptive Signal Control Technology (ASCT) for Traffic Signals

Two potential solutions are the addition of Automated Traffic Signal Performance Measures (ATSPM) or Adaptive Signal Control Technology (ASCT) to help smooth out and control traffic flow. Both of these solutions use multiple detection methods to gather real-time traffic information and monitor the signal system’s performance along an entire corridor. An ATSPM system relays that information to a traffic engineer or technician to monitor the signal performance and make necessary timing changes at an intersection based on that information.

ASCT systems allow individual signals to communicate with each other to smooth out traffic flow.

An ASCT system takes things one step further. Instead of sending the data to a traffic engineer for assessment, the information is evaluated by the system and signal timing improvements are developed by an algorithm. The ASCT implements the updates continually, sharing information between signals to make timing adjustments. These constant adjustments accommodate traffic patterns that are different from the peak periods (during which the standard signals were designed to operate) and help keep traffic flowing smoothly.

The transportation engineering experts with Snyder & Associates are well-versed at helping communities evaluate the factors that would lead to the requirement and implementation of an ATSPM or an ASCT system. Most recently, our team worked with the City of Waukee to implement an ATSPM system throughout the community with the option to add ASCT in the future. Likewise, we’re also helping the City of Burlington implement performance measures along the US Highway 61 corridor through town. These improvements could also lead to an ASCT system, if needed in the future.

Our experience with ASCT implementation is just as vast. Our team recently worked with the City of Pleasant Hill to address ASCT needs along the busy Iowa Highway 163 corridor and the Cities of Clive and Urbandale to spearhead the installation of an ASCT system along US Highway 6.

Systems Engineering Study Determines Need for ATSPM & ASCT

To determine if an ATSPM or ASCT system is necessary for a corridor, a systems engineering study is generally in order. A systems engineering study is a meticulous process that follows guidelines established by the Federal Highway Administration (FHWA) and is also a requirement of most state DOTs to be eligible for grants and other federal program funding.

Transitioning to an ATSPM or ASCT system typically requires updating traffic controller hardware.

Because there are numerous traffic signal management and adaptive control systems available, it’s critical to know the existing conditions of a corridor before issuing a Request for Proposals (RFP). To that end, a systems engineering study looks at peak/off-peak traffic conditions and studies turning movement counts along a corridor. A thorough study will also inventory the current signal controller equipment in use, the communications network in the area, and any geometric concerns that may need to be addressed at individual intersections. Additionally, other improvements to modify signal controller cabinet equipment or update the communication network in the area are considered. Fiber optic connectivity is a strong necessity for all ATSPM and ASCT installations to provide the level of communication necessary for optimal performance.

Physical Impacts of ATSPM Implementation

Implementing an ATSPM system along a corridor has an immediate and noticeable impact on traffic flow. Namely, a performance measures system allows agency staff to review historical traffic signal operations to confirm citizen complaints and monitor traffic signal operations to identify faulty equipment. Signal timing adjustments can then be made based on recent, continuous traffic conditions instead of the limited day traffic count.

Physical Impacts of ASCT Implementation

The obvious impact of the implementation of an ASCT system is fewer delays due to congested traffic, reduced fuel consumption, and fewer frustrated drivers. The improvements, however, extend to numerous other benefits including:

  • Managing the queueing issues at intersections
  • Detecting the changes in traffic conditions before and after special events
  • Accommodating peak traffic periods and real-time changes in traffic volumes
  • Quickly returning signal operations to normal coordination after disruption by pedestrian actuation and emergency vehicle preemption
  • Reducing delays for side street traffic along a corridor

Cost Savings of ATSPM or ASCT Implementation

The continued use of older traffic signal technology also incurs substantial costs to businesses and consumers. Inefficient signals account for more than ten percent of all traffic delays and congestion issues on major routes alone (source: highways.dot.gov). For consumers, this results in excessive delays and fuel consumption but for businesses, it decreases productivity and increases labor costs, which are ultimately passed on to the consumer.

Older signals also affect the costs of managing agencies. Personnel must be diverted from other tasks to respond to citizen complaints when traffic signals do not meet motorist needs. Personnel manually compile the data for transportation specialists who then analyze the data and develop updated signal timing using the traditional signal timing process before generating their recommendations. Because these specialists must balance the needs of one intersection against the requirements of an entire system, this is time-consuming and expensive.

On top of these practical benefits, automated traffic signal performance measures and adaptive signal control technologies are also kinder to the environment as previously noted. Using an ATSPM system allows traffic engineers to update signal timings based on current traffic counts, while the ASCT system automatically adjusts signal timings to reduce emissions of hydrocarbons and carbon monoxide from vehicles by eliminating constant stop-and-go traffic situations.

Real-time management of traffic systems is proven to work, yet these systems require knowledgeable and experienced experts to determine which one is the right solution for your particular situation. Snyder & Associates is working to help bring these technologies to the clients and markets we serve. The deployment of an ATSPM or ASCT system is a critical step toward providing improved capabilities that allow affected communities to proactively manage traffic, enhance operations, increase mobility, and reduce congestion. For frustrated travelers, the optimal balance of red light/green light distribution is the ultimate payoff.

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