If all goes according to plan, sometime Monday morning an $11 million monitoring system linked to about 100 cameras suspended 20 feet in the air will take control of traffic lights at 34 intersections on U.S. 1 and start deciding which ones will turn green.
The switch along eight miles of U.S. 1 will bring the biggest test yet for Miami-Dade County’s effort to ease gridlock through “smart” traffic signals, phasing out a system where the switch from red to green runs on automatic cycles based on engineers’ best guesses of commuting patterns.
Once the U.S. 1 system goes online between Southwest 98th Street and I-95, computers will take over most of the decision making when it comes to extending green lights to let slow-moving traffic clear out or for lengthening a red cycle when it’s bumper to bumper and intersections are jammed.
The main aim is to line up the sequence of green lights on U.S. 1 so that rush-hour commuters can drive through a maximum number of intersections without causing excessive waits at cross streets.
“You want cars to get the green, start moving, start approaching that intersection and have the green pop up so you don’t have to stop,” said Frank Aira, chief of Miami-Dade’s Traffic Signals Division. “You get a platoon of cars, and you want to move them as far as you can before it’s necessary for them to stop.”
Cameras and other sensors calculate vehicle speed and car counts at intersections, and that data helps the computer decide whether the current timing schedule looks ideal. If not, the computer will tweak the schedule for the next cycle of red lights and green lights running through the intersection. With “adaptive” signals, an intersection can experience four or five adjustments in a minute.
Motorists on U.S. 1 shouldn’t expect miracles. The county’s test stretch of “smart” traffic lights on Northwest 36th Street in the Doral area went live in 2016, and traffic administrators say drivers at rush hour on that one-mile stretch now go through about 10 percent faster. Aira said the end result was about one minute less on the road per day.
There can be hiccups. An earlier test of a different system on Southwest Eighth Street several years ago caused problems when the computer got too aggressive in crafting new patterns for the lights. Drivers used to the order of reds and greens were hitting the gas too early when the pattern suddenly changed.
Aira said the current county system only gives computers the option to change the durations of green and red lights, not their order in an intersection’s traditional cycle.
There’s also the issue of cross-street waits. The computer system’s prime directive is to speed travel time where there’s the most demand for crossing the intersection — that is, the busiest direction for traffic. Every time a light stays green for northbound traffic on U.S. 1 in the morning, another light needs to remain red. That could lead to longer than usual backups on side streets that cross U.S. 1 in an effort to move as many vehicles as possible during peak times.
“There are winners and losers,” said Mark Nogaki, senior vice president of sales for Econolite, the company out of Anaheim, California, that has the $11 million contract with Miami-Dade to install adaptive traffic signals on 11 of the county’s busiest stretches of road. “But the idea is: How do you mathematically move the most people?”
Miami-Dade already has cameras up and running on the South Dade busway, a 20-mile route that’s dedicated to county buses running parallel to U.S. 1 in South Dade. Those now allow express buses to trigger red lights to turn green once the vehicle gets within 1,000 feet of an intersection. The county says the average express-bus trip from Florida City to the Dadeland South Metrorail station has gone from 67 minutes to 50 minutes.
The U.S. 1 launch brings computerized lights to the busiest stretch of highway yet for Miami-Dade. Also Monday, adaptive signals are set to take over on Miami Gardens Drive, between Northwest 73rd Avenue and Northwest 87th Avenue.
Those would be the first of the two regular road segments outside of the Doral pilot stretch to have the new lights operating, though the equipment has been installed in nearly 300 intersections across Miami-Dade in preparation for a wider rollout of the technology.
Miami-Dade is soliciting bids for the $130 million second phase of the project, to expand the cameras to most of the 3,000 intersections in the county over five years. The project is funded by a half-percent sales tax for transportation that voters approved in a 2002 referendum. The ballot language included “improving traffic signalization” as one of the uses of the new tax.
Installing the first wave of equipment throughout the year led to concerns of new red-light cameras, enforcement devices banned by Miami-Dade, Miami and other cities. While the county’s police command center can take over the traffic cameras for surveillance during emergencies, they’re not used for any ticketing purposes, Aira said.
Even so, the electronic eye has motorists taking notice.
“There is a psychological effect to seeing it,” Aira said, saying the lights with cameras are seeing fewer vehicles “blocking the box” by getting stuck in intersections when traffic doesn’t move after a light turns red. “People behave better.”