Motorists in many U.S. cities are already familiar with the perks of intelligent transportation systems. Depending upon their degree of sophistication, ITS technologies include variable message signs, traffic signal and lane controls, real-time weather information, ramp metering and video monitoring of traffic and highway security. ITS data can be sent to first responders and mobile apps to help drivers navigate around accidents and peak-period snarls.
But the Colorado Dept. of Transportation aims to take ITS a step further. CDOT says that early next year it will pilot key pieces of an advanced traffic management program developed in Australia. The system—dubbed Managed Motorways by traffic engineers in Melbourne—uses a slate of ITS technologies to reduce congestion: on- and off-ramp metering, variable speed limits, dynamic lane control, expedited incident management and the use of hard shoulder lanes during peak periods, among others.
The key to the Australian program is that ITS technologies are linked in real-time using advanced proprietary algorithms that serve as the “brain” of the system. The algorithms transform formerly “dumb” freeway ramp meters into a smarter, more integrated set of controls that maximize volumes and manage speeds along an entire corridor.
The results of the Australian system have been dramatic: 25% more vehicle throughput during peak periods, a 50% reduction in overall travel delays through most corridors and 20% to 50% crash-reduction rates along some segments.
“With those results, we thought it was worth a try here,” says Ryan Rice, director of transportation systems management and operations at CDOT.
But the Colorado agency won’t implement the “full operational treatment” of ITS options used in Australia, says Joshua Laippley, CDOT’s chief engineer. Instead, the Colorado program, called Managed Corridors, will focus initially on improvements in ramp metering and other ITS devices along a 15-mile stretch of Interstate 25 through Denver. The traffic count in the corridor averages 240,000 cars a day, says Rice.
The first goal of the pilot program is to improve traffic data collection. “Because you can’t optimize ramp management as a holistic system without accurate data,” Rice says.
The system needs at least 90% to 95% accuracy of data to work well, he adds. Then the algorithm uses that information to automatically adjust the timing of all ramp meters in the corridor every 20 seconds, thus improving throughput rates. The south I-25 corridor was selected because most of the interchanges already have ramp meters in place. The target volume is a maximum of 2,000 to 2,100 vehicles per lane per hour.
CDOT will execute a $500,000 contract with engineering consultant Parsons Brinckerhoff this fall for design, and the agency is targeting full implementation of the pilot program next spring. Total cost is estimated at around $6.5 million, Rice says.
The initial phase will run for at least six months, he adds, with a three-month evaluation period. CDOT says it will be the first time the Australian system has been implemented in the U.S.
CDOT has not set specific targets for improved traffic flow in the corridor during the pilot. “We won’t get a 25% boost like the Australians,” Rice says. “It might even be less than 5%, but even 1% to 2% is a substantial improvement for most drivers.”
He also says that managed corridor systems “have the potential to reduce the need for capacity improvements. Because we’ll be using existing infrastructure much more efficiently,” he adds.
ITS systems will become even more important with the advent of driverless cars and “mobility services,” Laippley says. New technologies will allow engineers to predict reliable point-to-point travel times, implement crash-free lanes and even reduce freeway footprints. That’s because cars will likely be smaller, with less need for wide highway shoulders. “We could move from 12-ft-wide lanes to 9-ft lanes,” Rice says.
But those realities are down the road. Until more DOTs upgrade their ITS and intelligent infrastructure capabilities and improve data collection, “as engineers [where driverless cars are concerned], we’re stumbling around in the dark a bit,” says CDOT RoadX Program Director Peter Kozinski.