Self-Driving Cars. Seamless communication between vehicles and the roadside. The ability to multitask while driving from point A to point B reliably, safely and on time.
It all sounds a bit like the George Jetson future we were promised in the 1950s, minus the flying cars. The difference is — the connected vehicle/automated vehicle (CV/AV) revolution is happening now. But before it becomes a reality, the technologies that make it possible have to be vetted, validated and successfully implemented. And before that can happen, we have to have a reliable way to test those technologies.
The Texas A&M Transportation Institute (TTI) has developed an innovative platform for assessing the potential benefits of different CV applications, concepts and technologies in a controlled environment that’s as close to real-world conditions as possible. The first-of-its-kind approach — called CONVAS (CONnected Vehicle Assessment Simulation) — marries the cost effectiveness of computer simulation with actual roadway operations to produce an efficient, yet dependable evaluation mechanism for the Federal Highway Administration (FHWA). TTI has been developing the platform since January 2014 and demonstrated it for FHWA officials this week.
“The limitations of traditional simulation come from having to model every input to be as realistic as possible,” explains TTI Research Engineer Srinivasa Sunkari, principal investigator on the project. “For example, a traffic signal has to be simulated exactly—and the randomness of traffic and driver behavior makes that very difficult to do.”
To mitigate the effects of modeling while improving reliability under actual driving conditions, Sunkari and his team used hardware-in-the-loop (HITL) simulation. This approach introduces hardware components into the model. Devices like traffic control signals are fed information (e.g., simulated data indicating a vehicle is passing a detector) and the signals react in real time. That reaction is then fed back into the model, and the simulated vehicle proceeds or stops accordingly.
Sunkari and his team also developed an enhanced HITL simulation by incorporating an actual, connected vehicle on a roadway network into a simulation model and displaying simulated connected vehicles inside the real vehicle at the same time. This enables development and testing of advanced CV applications or strategies by allowing assessments of how connected vehicles respond to each other. This is the first time HITL simulation has ever been applied in this way.
To more accurately represent CV communications, TTI researchers integrated the commercial microscopic traffic simulator Vissim with the open-source wireless network simulator ns-3. Doing so enables simulated vehicles to adapt to circumstances in the driving environment as needed, providing a more realistic performance of CV applications in the simulation model. Like their application of HITL simulation, TTI’s integration of the two simulators had also never been done before.
“CONVAS provides the most advanced, realistic evaluation tool for emerging CV/AV applications that rely on wireless communications,” says Sunkari. “And in the future, that’ll be just about every aspect of our transportation system.”
On June 22, Sunkari and his research team demonstrated CONVAS to visiting FHWA sponsors at Texas A&M University’s RELLIS Campus. The field test confirmed the successful integration of the Vissim and ns-3 simulators and showed the seamless data flow between the simulation model and the test vehicle’s on-board unit.
With the delivery of CONVAS in December, the FHWA will have a way to test the realistic impact of wireless communications on the performance of large-scale CV applications while minimizing evaluation costs. Through simulation, technologies can be fine-tuned, and engineers can use the results to design advanced algorithms that, in turn, will govern how vehicles drive tomorrow’s roadways. In short, thanks to CONVAS, the wireless solutions connecting our future transportation system will be safer, more dependable and less expensive to build.
“The technology used in developing this platform will bring benefits in connected vehicle research for many years to come as we work to improve our transportation network to become a more intelligent, more reliable and safer system,” says FHWA Highway Research Engineer Peter Huang, who manages the Turner-Fairbank Intelligent Intersection Traffic Control Laboratory. “We look forward to seeing the final product from the TTI-led team later this year.”