By Rick Staigle
Who: Sugar Land (Texas) Public Works
What: Technology introductions and upgrades
Cost: $9 million over roughly a decade
Funding sources: Federal Congestion Mitigation and Air Quality (CMAQ) grants
Engineering consultant: Traffic Engineers Inc., Houston
Subconsultant: Civitium LLC, Alpharetta, Ga.
General contractor: TransCore, Houston
Five years ago Sugar Land, Texas, received an American Public Works Association Transportation Project of the Year award for taking a monumental technological and intergovernmental leap in less than a decade. Conceived to support development by minimizing congestion in the booming community, the city's traffic management system has spawned a multi-agency, multicity effort.
In 1990, Sugar Land had 30,000 residents. By 2000, fueled by a steadily falling tax rate, restaurants, retailers, and companies like Bechtel Equipment Operations and MECO Inc. moved in and their people followed. Population was up 158%, and would grow another 33% by 2010.
In Texas, communities with more than 50,000 residents must contract with the state DOT to operate and maintain state-owned traffic lights. In 1998, with the all-important population threshold closing in, the city council gave public works the OK to develop a traffic management system that would benefit surrounding communities as well as Sugar Land. At the time, Sugar Land owned and operated only one of the 65 signals in the city. An acceptable level of service was defined by whether or not it was working normally or flashing red.
Starting from virtually nothing — no equipment and almost no relationship with potential partners like the state DOT or the Houston-Galveston Area Council — public works developed a traffic management center (TMC). Eight employees work on projects that range from a three-tier wireless network to ensure police and fire communicate during emergencies to collaborating with the state and neighboring Missouri City to add fiber optic capability to the system.Building a data management center
By stressing that less idling would lower emissions levels, public works received a $1.4 million Congestion Mitigation and Air Quality grant through the local council of governments. That was enough to buy Naztec Inc. signal cabinet controllers and ATMS.now (ATMS is an acronym for Advanced Traffic Management Systems) software.
Working from the public works building on Gillingham Lane, traffic engineers monitor 11 signal subsystems with 10 broadband Integrated Services Digital Network (ISDN) lines leased from the local phone company at $100/month for each connection. These subsystems communicate with individual traffic signals via twisted pair copper communications cable, spread spectrum radios, or fiber optic cable, but Assistant Public Works Director David Worley says the plan is to phase out ISDN entirely.
Traffic engineers installed a Cohu Inc. Electronics Division CCTV camera and Microwave Data Systems spread-spectrum radio antenna at 14 key intersections. Simtraffic Synchro 7 TrafficWare models signal timing based on vehicle counts collected by a controller in the signal cabinet, and Naztec's software downloads revised timing plans back to the controller.
They also developed an online “congestion index interactive map” based on travel time averages using the system's loop detection and vivid systems to count vehicles in addition to detecting their presence. They wanted to make the map available to residents on the city's Web site, but this didn't happen.
“Live traffic feeds are a nightmare,” says Worley, who was hired in 2008. “It bogs the system down and is difficult to manage.”
Almost no sooner was the system up and running, however, than the local council of governments approved their $1.9 million grant request to upgrade the system to a wireless network.
Signals that weren't on the system are being brought on board and more CCTV cameras deployed so engineers can watch traffic flow and modify timing plans based on congestion, traffic patterns, or incidents. The ability to instantaneously adjust flows maximizes current road capacity, freeing resources for other public works projects by reducing the number of required widening projects.
A wireless backbone (see image on this page) was designed using eight high sites on water towers, buildings, and one new self-supporting tower. The 11-GHz microwave point-to-point Motorola Solutions radios will tie to the city's existing fiber network at City Hall and Fire Station #2. A ninth high site has been added to the plan to serve an area that was annexed in 2009.
The high sites will communicate with all of the city's traffic signals via 4.9-GHz Motorola Solutions point-to-multipoint radios. Half the intersections also will be equipped with IP-addressable Axis Communication's CCTV cameras with H.264 video encryption and 2.4-GHz Motorola Solutions Wireless Access Points (WAP) so technicians can log into the network from the field, reducing aircard expenses. The remaining intersections will have some combination of signal controller communication and, possibly, CCTV cameras.
If additional bandwidth is needed before the fiber optic system's completed, more point-to-point and point-to-multipoint radios can be added to the network.
Nine older signal controllers and cabinets are being replaced with TS2 Ethernet controllers and the faceplates on 35 TS2 signal controllers are being replaced to make them Ethernet controllers. This will allow the controllers to more efficiently interface with the switch and, ultimately, the 4.9-GHz radio. Half the cabinets had switches and the rest will get Cisco Systems Inc. switches.
One intersection exceeded the distance limitations for the Ethernet cable and will use multimode fiber for communication between the CCTV cameras and the switch, and from the switch to the 4.9-GHz radio. Two locations where cameras were located away from an intersection will connect the cameras directly to the radio to communicate directly to the high site, bypassing the signal controller cabinet.Moving toward regional mobility
In the meantime, the team has been overseeing projects that facilitate traffic flow in other ways.
Sugar Land built the state's first triple-left-turn lane, from U.S. 59 to State Highway 6, which passes major retail and restaurant centers on its way to a regional airport. A dynamic message sign and LED lights installed in the pavement guide drivers more efficiently through the intersection.
About 40 trains pass through Sugar Land every day. Quiet zones and wayside horns were installed for the rail line along the US 90A corridor in 2009; and two timing operations — one for trains that cross intersections within two minutes, the other for trains that take longer — were developed to quickly transition back to normal traffic signal coordination.
Other intelligent transportation projects include:Reconfiguring key intersections along S.H. 6 near U.S. 59 with video detection capability so signals automatically adjust in real time based on traffic demand.Implementing flashing yellow arrows for permitted left-turn movements at several locations to determine whether to deploy systemwide. Allowing permitted left turns reduces delay at the intersections and research has shown that the flashing yellow arrow has fewer crashes than the older, green ball signals used for left turns.Installing 1.25 miles of fiber optic line on SH 6 between city hall and the police and courts building that will replace an existing leased line where the lease expires in 2012 and extend into neighboring Missouri City.
As the latter project suggests, Sugar Land and its neighbors are working toward being able to offer residents and visitors multimodal transportation options. Though a long-term goal, partnerships the city's forged over the last two decades are facilitating the coordination of related efforts in the region. For example:Agreements are being finalized to provide fiber optic connections to the state DOT at the intersection of US 59 at SH 6, allowing Sugar Land to become a hub of TranStar, the primary traffic management center for the Houston region.The fiber optic connection being installed along SH 6 will connect to an existing fiber optic line in Missouri City, enabling TMC-to-TMC communication between the two cities.Communication links with the Fort Bend Emergency Management Center are being developed.Discussions have begun with the City of Meadows Place to bring the West Airport signal into Sugar Land's three-tier wireless system to coordinate traffic flow between the two cities.
By leveraging existing and future equipment, the cities, county, and state will improve quality of life by reducing travel time and delay.
— Staigle (firstname.lastname@example.org) is a principal with Traffic Engineers Inc.; Johnston is editor in chief of PUBLIC WORK.WEB EXTRA
To read a white paper Rick Staigle presented on how to construct a wireless communication network at ITS America 2010, Houston, and at ITS World 2010, South Korea, click here.