The current systems used to communicate between transportation field elements, such as Road Weather Information Systems (RWIS), sensor networks, and Changeable Message Signs are dependent on leased services that may include cell phone technology, or private telephone lines. The leased services can be unreliable, and often times unavailable in rural, less traveled areas. Areas where the ability to communicate and gather travel information is critical field crews that increasingly base winter highway treatment decisions and traveler information on reliable communication systems. In addition to access challenges, there often are recurring costs associated with leased services, and these costs may hinder the addition of field elements required to adequately monitor a corridor or specific areas of a roadway. Many DOTs have invested heavily in radio communications systems to support their field staff during their daily activities and during incident response or emergencies. With the proper planning and design, the same communications system can be used to acquire and provide information from the field elements. Radio communications traditionally have a proven higher degree of system performance and reliability than leased services.
The proposed research will help DOTs leverage existing communications systems to acquire and provide reliable and timely information from field elements using the 700 MHz radio spectrum. Using that spectrum also may provide interoperability with the federally planned Nationwide Public Safety Broadband Network (NPSBN or FirstNet), which utilizes Band 14 (758-798 MHz). The NPSBN will provide data communications services, including video, to public safety providers throughout the nation. PSBN (FirstNet) will begin implementation in 2017. The start dates for each state will vary as some states are further ahead in the process than others. There is an “opt-out” option for each state—meaning states can deploy their own network in lieu of FirstNet, but approval from FirstNet is required.
700 MHz was selected for this potential research project for the following reasons:
- The FirstNet system will also be utilizing the 700 MHz band, and this will allow interoperability, and
- 700 MHz channels became available when cable TV (channels 60-69) converted to digital.
If a state has radio infrastructure on another radio band (150/450/800 MHz), they can leverage those assets instead of 700 MHz. The project also should determine how many states have access to a 700 MHz radio network and what the associated costs would be to connect to field devices. As part of this research, a proof-of-concept study will be performed with various field elements, providing information through a 700 MHz radio system. This capability also can be used as a backup to essential assets that may be impacted by the private leased services. Caltrans has an 800 MHz, 2-way land mobile radio installation along Hwy 199. The radio equipment is housed in a standard traffic cabinet, while the antennas and wind generation are on a 30-foot pole; a similar approach could be followed for the RWIS, or other field elements, where feasible.
If the radio communications platform is capable of providing the communications required by the field elements, State DOTs will achieve significant savings by eliminating leased service fees, and at the same time, operate a more reliable communications system. Communication systems are the backbone of emergency management and infrastructure protection coordination. These systems enhance resilience. This project can help with other AASHTO and TRB research efforts, such as FloodCast, FireCast, ShakeCast, and it can help to mainstream emergency notification systems as well.