For DSRC communications, message exchanges should be managed using channel diversity and varying power levels appropriate for the spatial density of the roadside units (RSUs)
- The reliance solely on DSRC communications for all vehicle to roadside (and vehicle to CV system) communications created challenges for the NYC Pilot. The NYC project will use six of the seven DSRC channels for all the V2V and V2I applications and messages (BSM1, SPaT, MAP, RTCM, TIM) and using CH178 as the control channel to direct the on-board units to switch to other service channels for over-the-air software updates, security credential distribution, and data collection. NYC block spacing is approximately 72 meters (N-S) and 200 meters (E-W), hence the need to deal with the overlap of signals and saturation at some locations with a high density of test vehicles. NYCDOT will be managing the transmit power and monitoring the system operation very carefully to ensure that the V2V and V2I safety applications work as expected.
Formulate data collection procedures that account for bandwidth and privacy limitations
- Where previous CV R&D projects collected every BSM, SPaT, MAP, and other messages transmitted and received by all devices (RSU and After Market Safety Device (ASD)) for analysis, the NYCDOT does not have the bandwidth, and there were major privacy concerns if such information is stored and becomes available for subpoena or freedom of information retrieval. If one combines the 10 Hz BSM information with the police records, there is concern that this could violate the privacy requirements even with the changing credentials and changing MAC addresses. NYCDOT devised a mechanism for selectively monitoring the subject vehicles by keeping a 5-minute rotating log of messages transmitted and received from "nearby" vehicles and intersections. When an incident occurs, contents of the log immediately before an alert is issued (~10 seconds–configurable) and immediately after the alert (~20 seconds) are captured to form an "event record" such that NYCDOT we can evaluate the parameters that caused the alert as well as the driver's reaction, thus measuring the safety benefits. The data collected is encrypted on the vehicle and transmitted (via the RSU) to the Transportation Management Center (TMC) where it is decrypted, verified, normalized, obfuscated, and analyzed to measure the benefits.
- The NYCDOT currently operates an adaptive traffic control system that uses vehicle speed (travel times) and occupancy measured with radiofrequency identification (RFID) readers and microwave vehicle monitors. NYCDOT will be evaluating the effectiveness of the CV data by sending the traffic management center a single BSM from each vehicle as it passes through the intersection. NYCDOT plans to use this to measure travel times and to evaluate the CV data's effectiveness when compared to the RFID information for providing the input to the adaptive control algorithms.
Manage the operations and management health of the system elements using a tool that provides measurements in near real-time
- NYCDOT has introduced a number of applications intended to allow the TMC to monitor the "health" of the ASD and RSU; the RSU will monitor the BSMs received while the ASD will monitor the SPaT and MAP messages received and record the first and last message heard along with the radio frequency level of the received signal. Using this data, the TMC can construct a "scatter graph" of the effective communications pattern around each RSU and each ASD. This will allow NYCDOT to determine when one or more transmitters appear to be "inactive" or "weak" for pro-active maintenance. It is important to note that such measurements are made in near real-time and sent to the TMC when in range of a support RSU. This provides a maintenance tool to determine when to bring a vehicle into the shop for evaluation and repair and when it is operating properly.
Supplement location systems with any needed corrections to improve the vehicle's ability to monitor its position accurately in the urban "canyons" and underpasses
- The current standard for On-Board System Requirements for V2V Safety Communications (SAE J2945/1) requires the vehicle to cease transmission if it loses GPS "lock," which is not practical in the dense urban environment. For NYC, the vendors were required to augment their location determination algorithms to include inertial navigation, map matching, tethering to the vehicle, and RSU triangulation. Preliminary testing indicates that this combination, with the proper algorithms and tuning, will meet needs and continue to be evaluated during the project.
Adopt over-the-air techniques for updating equipment firmware to cut down on the time and expense needed to administer such updates to vehicles
- NYC has been working with the vendors to develop a general purpose over-the-air (OTA) technique for updating the ASD firmware using the DSRC communications while the vehicle is within range of a "services" RSU. Because of the number of vehicles involved in the project and the need to proceed with the installation without all of the applications fully operational and update them during the integration period, the NYCDOT is working with the vendors such that they will generate the updates and demonstrate them to the City before launching the full complement of applications prior to the evaluation period. Hence, testing of the "platform" and the reliability of the OTA update procedure will be extensive since the NYCDOT cannot afford either the time or expense to visit the vehicles to administer such updates.
Install vehicle on-board equipment that minimizes driver distraction
- For the NYC pilot project, all alerts will be provided using only audio tones and words. The fleet vehicles already have a significant number of "cockpit" displays and, with the concern over driver distraction, the stakeholders did not want another distracting display for these applications. As a result, the ASD for NYC will include stereo speakers that will support text to voice, tones of varying pitch a frequency, and a combination of both, which were well received during the demonstrations of the devices. The in-vehicle system also includes a microphone that can evaluate the background noise level and adjust the audio output as necessary and verify that the intended alert message was delivered to the driver.
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