The rapid growth of traffic-related fatalities and injuries around the world including developed countries has drawn researchers' attention for conducting research on automated highway systems to improve road safety over the past few years. In addition, fuel expenses due to traffic congestion in the U.S. translate to billions of dollars annually. These issues are motivating researchers across many disciplines to develop strategies to implement automation in transportation. The advent of connected-vehicle (CV) technology has added a new dimension to the research. The CV technology allows a vehicle to communicate with roadside infrastructure (vehicle-to-infrastructure), and other vehicles (vehicle-to-vehicle) on roads wirelessly using dedicated short-range communication (DSRC) protocol. Collectively, the vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communication technologies are known as V2X technology. Automotive companies have started to include On-Board Units (OBUs) on latest automobiles which can run safety-critical and assistive applications using V2X technology. For example, US Department of Transportation has already launched various applications including but not limited to lane-change assistance, collision avoidance, SPaT for emergency and transit vehicles. Merge conflicts, especially when vehicles are trying to merge from ramps to freeways, are a significant source of collisions, traffic congestion and fuel use. This paper describes a novel freeway merge assistance system utilizing V2X technology with the help of the DSRC protocol. The freeway merge assistance system uses an innovative three-way handshaking protocol and provides advisories to drivers to guide the merging sequence.
The rapid growth of traffic related fatalities and injuries around the world including developed countries has drawn researchers' attention for conducting research on automated highway systems to improve road safety over the past few years. In addition, fuel expenses due to traffic congestion in the U.S. translate to billions of dollars annually (1). These issues are motivating researchers across many disciplines to develop strategies to implement automation in transportation. The advent of connected-vehicle (CV) technology has added a new dimension to the research. The CV technology allows a vehicle to communicate with roadside infrastructure (vehicle-to-infrastructure), and other vehicles (vehicle-to-vehicle) on roads wirelessly using dedicated short-range communication (DSRC) protocol. Collectively, the vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communication technologies are known as V2X technology. Automotive companies have started to include On-Board Units (OBUs) on latest automobiles which can run safety-critical and assistive applications using V2X technology. For example, US Department of Transportation has already launched various applications including but not limited to lane-change assistance, collision avoidance, SPaT for emergency and transit vehicles. Merge conflicts, especially when vehicles are trying to merge from ramps to freeways, are a significant source of collisions, traffic congestion and fuel use (2,3). This paper describes a novel freeway merge assistance system utilizing V2X technology with the help of the DSRC protocol. The freeway merge assistance system uses an innovative three-way handshaking protocol and provides advisories to drivers to guide the merging sequence.
Vehicles equipped with V2X capable OBUs transmit basic safety messages (BMSs) every tenth of a second. A BSM packet includes a vehicle’s identifier, GPS positions, speed, time, and direction. The freeway merge assistance system utilizes these BSM packets and determines the optimal merging order for drivers using a 3-way handshaking communication protocol. Overall, the freeway merge assistance system performs the following steps to determine the merging order and generate advisories for drivers.
Transmission and reception of BSM packets. The transmission module of the freeway merge assistance system transmits the BSM, following the updating time of the GPS. The receiver module receives BSM packets from the surrounding vehicles within a range of 300~500 meters (5). Both modules use a singlehop communication protocol (6) for transmitting and receiving the BSM packets.
Observation of vehicular trajectories. The freeway merge assistance system considers the ramp vehicles as the master vehicles who initiate all communication. A ramp vehicle triggers the core algorithm of the freeway merge assistance system as soon as the ramp vehicle enters into a ramp, notifying all the vehicles around notifying that a new vehicle entered the ramp. The data collection unit of the system collects and stores the vehicular trajectories of all the surrounding vehicles.
Calculation of the merging order. The data processing unit of the system filters out the noisy data from the collected trajectories and estimates the future trajectories to determine the merging point where all the ramp and freeway vehicles could meet. The unit also determines the approximated time for each vehicle to reach the merging point. Once the unit determines the time for each vehicle, the freeway merge assistance system initiates a three-way handshaking communication protocol (as illustrated in Figure 1) to transmit the timing information to all in range vehicles.
Generation of advisory messages. The freeway merge assistance system will then request a synchronization with the remaining vehicles to ensure they all in-range vehicles have the same timing information. Finally, when all the vehicles have mutually acknowledged and accepted the merging sequence, the freeway merge assistance system triggers the advisory generation module on each vehicle.
Once the merge assistance system is ready to generate the advisory messages on each vehicle, it will send the information to a map application on an Android device using Bluetooth connectivity. The messages will advise each driver according to the previously defined merging sequence and they will be displayed over a map marker with a text message. The application will also highlight the map marker (using a larger-size marker) for any referenced vehicle, e.g., if a vehicle on the freeway need to slow down to allow a ramp vehicle to merge first, the application will display the “Slow down” message to the freeway vehicle showing a larger-size map marker for the ramp vehicle on an Android device. Similarly, the application on an on-ramp vehicle may display the “merge behind” message showing a larger-size map marker for the freeway vehicle that the ramp vehicle will need to follow.
To evaluate the feasibi
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