The Federal Communication Commission’s final rule to reallocate 45 megahertz of the 75 megahertz previously allocated to transportation safety went into effect in early July. The rule is being appealed in the U.S. Court of Appeals for the D.C. Circuit, but, in the meantime, cities are experimenting with other types of technology.
When reallocating the spectrum, the FCC also specified a particular technology for the remaining spectrum. Transportation safety must use a technology, LTE cellular vehicle to everything (C-V2X), which is still undergoing testing by the U.S. Department of Transportation, rather than the tested, proved, and licensed technology, Dedicated Short Range Communications (DSRC). If the court appeal does not succeed, then C-V2X will be the only permissible technology, and the deployments of DSRC will have either to move to C-V2X or to be abandoned.
Last week Applied Information, a transportation technology developer, held a webinar on C-V2X connected vehicle applications. Applied Information president Bryan Mulligan demonstrated how C-V2X technology could work in a positive manner to preempt traffic lights for emergency vehicles and school buses and to enable cyclists and pedestrians who had an app on their phones to be warned about accidents.
In a phone call on July 28 Mulligan told me, “Today’s connected vehicle applications require more than one communication technology to create a safer mobility experience. Long-range communications, such as 4G or 5G, enable pedestrians and cyclists to use their cell phones to communicate with vehicles and to avoid crashes. Short-range, direct communications between vehicles and the infrastructure such as C-V2X help prevent crashes and dangerous situations between vehicles such as red light running, school bus stop arm violations and speeding in school zones.”
All across the country cities are testing different technologies which are being licensed by the FCC on an experimental basis. Some fixed systems have hardware that controls traffic signals, school zone safety beacons, pedestrian crosswalks, rail crossings, and message signs. Mobile infrastructure is placed in government-owned vehicles such as fire apparatus, police cars, snowplows, school buses and ambulances. Cell phone apps connect others to the systems.
Earlier this month Cary, North Carolina, chose Applied Information for a $2 million project to upgrade its traffic control system using a C-V2X network. When complete, the project will connect traffic signals with pedestrian and rail crossings, and school zones safety beacons. Residents can install a TravelSafely® smartphone app on their phones to be connected to the system.
Honolulu, Hawaii, is developing a similar system to improve traffic flow and safety at a cost of $6 million, mostly funded by the U.S. Department of Transportation. The program, using technology by Econolite, Goldwings Supply Service, Inc, and Qualcomm
The Intelligent Transportation Systems of America (ITSAmerica) and the American Association of State Highway and Transportation Officials (AASHTO), which are challenging the FCC in court, want the full 75 megahertz to be used for transportation safety—while still allowing C-V2X to be used on the upper portion of the band. If they win, then two technologies will operate in parallel: DSRC on the lower part of the band and C-V2X on the upper part. The U.S. Department of Transportation Safety Band website lists over 75 DSRC deployments.
Because C-V2X relies on cellular network connections sending signals many miles between two cars, signal delay may be greater than with DSRC technologies that send signals directly from one car to another.
C-V2X applications could work well for applications such as changing traffic lights, because the risks associated with slight signal delays could merely mean a school bus might face an additional red light.
However, for safety of life applications where a thousandth of a second matters in preventing an accident, C-V2X might work less well than DSRC even if C-V2X systems work perfectly. But there is reason to expect C-V2X systems may not work well all the time. Everyone knows that messages on smartphones can be delayed by extra network traffic or dropped signals.
Automotive safety technology advances rapidly, but challenges remain. For example, vehicles are being equipped with cameras which are supposed to recognize hazards and, when necessary, to brake immediately. However, you would not want your car to brake suddenly when a plastic bag flies across the road. As it is, some new vehicle cameras cannot see cones in work zones.
The DSRC system is an elegant low-cost solution that solves multiple problems in the same way that penicillin takes care of many illnesses. It has no delays, it is affordable, it works for safety and for traffic priority, it takes care of fuel efficiency, it is good for the environment. Without DSRC we will need multiple systems with interconnecting parts that might not be as reliable for all purposes. The good news is that the systems and the technology are rapidly developing.