Test of bilateral preference communication using V2X – verification of  controlled t stationing principle

Test workplace at the intersection.

A successful test of possibly the first bilateral communication between an intersection controller and an UPT vehicle ( controlled stationing) took place on  4.10.2019 in Ostrava. It was supported by Ostrava City Authority,  Ostravske komunikace, and Dopravní podnik Ostrava a.s. (DPO). the goal of this test was to try out a new type of preference communication via V2x (standard ETSI ITS G5) which would be able to replace the current communication via a 160 MHz radio station.  We are talking about controlled stationing – principle and advantages are described here . 

Controlled stationing test conditions

The tests of the functionality of public transportation vehicle preference (DPO vehicles) in the form of  controlled stationing  using V2X (C2X) communication technology took place on  4. 10. 2019 at the intersection 4077 – st.  Martinovská x Provozní. The time of the test is about 10:15 – 11:15.  SW support of preference using V2X in the form of modifications of programs of  on-board computers EPIS  and OBU units (UCU 5.0 xx) was implemented in all UPT vehicles of DPO, a.s, i.e. each passing DPO vehicle had the ability to request preference (all DPO vehicles are equipped with V2X units).

Simultaneously, the intersection controller was connected to an RSU unit (UCU 5.0) via RS-485 interface. The unit communicated with the controller. The RSU unit used V2X communication to receive commands from vehicles and send replies from the controller to the same vehicles including commands to leave the station obtained directly from the controller (stationing). All passing DPO a.s. vehicles with set line and connection requested preference. Vehicle  7181 was chosen for further tests. The OBU unit (On-boad unit – unit for V2X on the DPO,a.s vehicle,  UCU 5.0 LWVG)  sent commands to the RSU unit via V2X as per commands from the on-board computer (EPIS 4.0x). The RSU unit delivered the commands to the controller.

Other conditions of the controlled stationing test:

1. The V2X communication worked as per the new norm C-ROADS and the publicly known protocol from the Herman company (preference specification) – valid for the vehicle unit (OBU) as well as for the intersection unit (RSU).
2. The on-board computer EPIS 4.0B was equipped with a control program with “parallel communication”, i.e. via standard radio memo communication and via V2X (the on-board computer controlled both preference systems at the same time).
3. The UPT vehicle informed its surroundings about its arrival to and departure from the station, about its door opening and closing, etc. see TS G5 standards.
4. Communication with the intersection controller worked as per the existing principle (SW controller was not changed).

Principle of controlled stationing (bilateral communication vehicle-controller)

The main reason for this test of controlled stationing was verifying that the V2X principle supports bilateral communication between a vehicle and an intersection controller in such way that not only preference request receipt by the controller is confirmed, but also the stationing principle is supported. This term is used for situations when the controller actively controls the behavior of a vehicle at a stop.

Pic. no. 2: Vehicle stationing at stops for UPT preference.

The stationing principle is as follows:

1. The vehicles announces its arrival to the station situated in front of the intersection to the controller – Picture 2A).
2. The controller sends a command to wait for a command to leave the stop to the vehicle – Picture 2B).
3. The vehicle stays at the stop and can take up passengers, when the passengers are in, the vehicle waits for the controller to provide information about a future green light.
4. The controller send a command to leave the stop to the vehicle. This command is sent at a time when the controller is ready to give a green light, Picture 2C).
5. The vehicle leaves the stop and informs the controller about this action. At that moment, the controller starts changing its signal plan to provide the vehicle with the green light.  Picture 2D).
6. The vehicle passes through the intersections and informs the controller about that.

All the communication was performed via V2S and SRM and SMM messages.

Progress of the test

The UPT vehicles of DPO a.s. were passing through the intersection with a set service (line, destination). 16 different vehicles (buses and trams) passed through the intersection. Some of them including the test bus went through the intersection multiple times (they turned around at the terminus).

During each passing, all preference commands sent by the  EPIS 4.0B on-board computer got to the controller where they were interpreted correctly and preference was activated. The request processing status was sent by the controller to the RSU unit and the RSU unit sent it to the UPT vehicle  via V2X. The OBU unit in the vehicle (UCU 5.0 LWVG) processed this message correctly and prepared it to be handed over to the on-board computer (in the case of controlled stationing). The on-board computer received and processed the message from the controller including the command to leave the stop. In all the observed vehicles, the command to leave the stop was displayed (a green bar on the EPT 4.08 terminal). During the test, 91 preference commands were sent by 16 vehicles, and all of them were confirmed by the controller. 14 commands to leave the stop were sent while the number of announced arrivals to the stop was also 14.

Results of the controlled stationing test

The result of the test was positive, bilateral communication via SRM and SSM messages fully replaced the existing communication via a 160 MHz radio network. It was confirmed that V2X can be used for preference even for existing preference systems including the function of bilateral communication and “controlled stationing” (a description of the functionality of unilateral communication vehicle-controller is here).

All events at the intersection were monitored by our program  V2Deep, description here. It would be very difficult to monitor events at the intersection without this program.

Pic. no.3: An example from the“V2X message visualization” – SW V2Deep during the test of preference at interactions.

V2X communication range at the test location

It should be taken into consideration that the RSU unit was not placed on the traffic lights post, it was placed on the distributor case (see the introduction picture). As a consequence, the range was shorter than it would be in real operation. The actual ranges were 300 meters to he South, 500 meters to the South-West and 250 meters to the West. We can conclude that considering the chosen preference mode the ranges were fully satisfactory.

Pic no.4: Detection of the first message via V2X from a vehicle – the vehicle sends the information about its position periodically at least 1x a second (these are not preference messages, those are sent at a request).

Pic. no. 5: Detection of the last message from a vehicle before the signal was lost. The vehicle sends the information about its position periodically at least 1x a second (these are not preference messages, those are sent at a request).