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Broadband Access
City of Sacramento alleviates drivers' gridlock with Ethernet
Network provides traffic department greater bandwidth and increased visibility
by Sean Buckley
Managing traffic congestion is an ongoing issue for every U.S. city and town, and Sacramento, Calif., which has seen sharp increases in its own traffic and population over the past ten years, is no different.
In fact, a Texas Transportation Institute mobility study says that Sacramento ranks in the top 30 of the most congested cities in the U.S.
But Sacramento has two weapons to battle the traffic bulge: its own fiber and copper-based telecom networks. It is leveraging these assets to build out an Intelligent Transportation System (ITS).
To build out an ITS, cities and towns will deploy a mixture of dynamic message signs, IP video monitoring cameras and sensors in existing street signal cabinets. Increasingly, the underlying technology used to connect this new infrastructure is Ethernet.
Like other communities, Sacramento traditionally managed its traffic signals via dial-up modem links that operated at speeds as low as 1200 bps. As the city started to install IP-based cameras and controllers, the city's traffic department would require more bandwidth thana dial-up modem could never handle.
“The whole system is moving to IP, so we needed bigger pipes, and had to bring in new controllers,” said Shad Bennett, head of traffic engineering and operations for the City of Sacramento.
Buoyed by the new government-driven initiatives such as the Obama administration’s Main Street Recovery program, cities like Sacramento are IP-enabling their traffic controllers, while simultaneously installing cameras at each traffic light to monitor traffic flows.
Due to the accelerated time for deployment that the stimulus package requires, Sacramento is currently not going after that funding. Instead, the city is leveraging other federal and state funding grants for its projects.
“There are some stimulus monies that are coming down the pipe, but we’re not going for the stimulus money because they want something quicker than what we can turn around right now,” Bennett said.
Copper hits the spot
To IP-enable its traffic controllers at the signal cabinet, Sacramento’s traffic engineering department initially connected these controllers and cameras to fiber rings that resided close to the sites where the cameras were located.
And while Sacramento has a good amount of fiber, it does not reach every location. Building a business case to bring fiber to remote areas of the city is just not feasible.
Sacramento, however, found its miles of existing copper wiring was its saving grace.
Unlike some cities and towns that rent copper and fiber from the local phone company, Sacramento actually owns its copper and fiber infrastructure.
Similar to other nearby cities, Sacramento deployed Actelis’ ML series of Ethernet Access Devices (EAD) at traffic sites in a hub-and-spoke network configuration. In a traffic application, Sacramento could also use the system for red light speed enforcement and Dynamic Message Signs (DMS).
Being able to plug the Actelis gear into its existing copper network continues to come in handy. In remote areas where the existing remote conduits are too small or old to replace with fiber, they will daisy chain those cabinets with Actelis’ Ethernet over Copper system.
Leveraging existing copper, some of which can be decades old, brings with it relative unpredictability. Actelis’ gear can expand the amount of bandwidth through its intelligent power back-off feature by mitigating crosstalk that could arise between existing copper pairs.
“We have different signals, including signals that come through our office,” Bennett said. “Each one is looked at on a case-by-case basis, but a lot of times if we don’t have the fiber infrastructure in place, we’ll try to leverage our existing copper infrastructure to bring IP communications out to these signals.”
What ultimately determines the use of fiber or copper in a particular project is the scope of the project, location, and of course cost.
“A lot of times, the copper infrastructure is already there because back in the 70s, 80s and 90s, we made sure that every signal we put in was interconnected with copper,” Bennett said. “Chances are if we want to put in a new signal together, we can run a quarter mile run down to the next signal and we’ll have a copper path from our central location out to the outskirts of town.”
IP enhances visibility, bandwidth
Traditionally networked with dial-up 1200 baud modems, Sacramento's IP drive was sparked over ten years ago when it began installing surveillance cameras in its network. These cameras were initially installed on Sacramento’s own fiber-based rings to measure the effects of traffic during morning and afternoon commutes.
Once the city got the fiber connections in they could not live without them, but “the only thing is fiber isn’t available everywhere,” Bennett said. “Really, it was the cameras that spurred on the need for higher bandwidth. Once you’re there with high bandwidth, meaning IP, it does not make sense to have a serial connection plus a fiber connection to the signal cabinet.”
Going to an IP-based network provided Sacramento with various benefits.
For one, it gave the city increased bandwidth and the ability to consolidate all of its signal equipment onto one common IP connection. By leveraging Ethernet over Copper gear, Sacramento can at least enhance various sites with IP today instead of waiting for a feasible business case for fiber to appear in the future.
Having a high-speed IP and Ethernet-based network enables the city’s traffic engineering department to gain better visibility into the equipment that resides at the signal cabinet, particularly the IP cameras in its network.
This means that if a traffic signal fails, a technician at the city’s Traffic Operations Center can respond to the outage more quickly. By optimizing traffic flows, the city can then decrease the amount of time a commuter is idling in their car.
“What ITS enables us to do is to talk to everything that’s in that signal cabinet,” Bennett said. “On one occasion we have Wavetronics account station meters that plug into an IP port, which allows us to then pull back that information to a central site. Then, all of the cameras are encoded right there at the cabinet and transmit information back via IP.”
Regardless of whether the communication scheme is IP or TDM, the key factor is being able to see the signal.
Now technicians at the central location understand the nature of the signal: flashing, stopped, preempted, or is the detection working properly.
Having this visibility would be beneficial during road construction projects in each zone.
“If the city is doing some street widening or there’s a construction crew doing some work in the lane, you can remove that zone remotely,” Bennett explained. “You don’t have to send a whole crew there and I can manipulate the signal so that construction will be minimized so I can get the traffic through without significant delays.”
What’s more, the IP-based cameras allow traffic technicians to perform instant analysis of traffic flows.
After changes are made, technicians can also watch traffic patterns on a screen in real-time and see what the changes are doing to the traffic in the area — something that was near-impossible with traditional dial-up modems.
Sacramento and other cities' efforts to make the migration to IP is not only transforming their own network, but also influencing traffic signal industry to make their products more IP-capable.
“You can now get quality data back whether it's account stations or video, but you’re not dealing with that bottleneck of 1200 baud modems that were the norm just five years ago,” Bennett said.
Agencies take notice
Designed to be invisible to the public, the ITS monitoring and surveillance network is now getting the attention of other agencies in Sacramento.
Bennett admits that while Sacramento has made marked progress in IP-enabling its traffic system, he’s quick to point out that other local cities such as Roseville, Calif. are slightly ahead.
Nearby Roseville has, for instance, integrated the data they gather from their traffic signals to go to their website and watch real-time video on the city’s traffic conditions.
“It’s further than we are right now, but we’re not too far behind since we have a few of these [Actelis] units deployed when we’re on the outer edge of our network,” Bennett said. “The county and Elk Grove are also using Actelis gear. We’re all kind of growing at the same spot, but each agency is picking and choosing what technology works best and slowly plugging along.”
Nonetheless, the IP network is attracting the attention of other local agencies in Sacramento, including law enforcement.
Law enforcement plans to leverage the network's cameras for their own surveillance needs.
Following the lead of other large cities such as New York and London, both of which have leveraged remote cameras to enforce toll roads, speed limits and lane restrictions, Sacramento’s law enforcement agencies could use the cameras to conduct real-time traffic monitoring, with automated plate recognition to track suspect vehicles.
“We are looking to use the network for other surveillance purposes, and can cost-effectively deploy cameras and other broadband tools using our existing copper infrastructure,” Bennett said.
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