Communication V2X in public transportation

Pic. no.1: The divided version of the communication unit on a DPO plc. bus

The V2X technology brings brand new possibilities in public transportation and it integrates the current functions of communication with close surroundings into one radio technology. One communication unit provides functions previously performed by numerous devices. Moreover, everything is realized in accordance with international standards which ensures interoperability among individual manufacturers. 

Possibilities provided by V2X units in public transport

Most of the possibilities offered by V2X to public transportation can only be realized based on interaction between an OBU unit (unit UCU 5.0 in our production) and an on-board computer (on-board computers EPIS 4.0x or EPIS 5.0x). As we supply both on-board computers and OBU we are able to ensure this close cooperation even including the connection to all needed preparation SW –  EPCOMP and BOS  in a more general conception.

We offer solutions of the following situations in public transportation (PT – both municipal and regional):

• Vehicle preference at intersections –  an OBU unit installed in a PT vehicle is commanded by an EPIS on-board computer and uses V2X to send an intersection preference request. This request is received by an RSU at the intersection which transfers it to its intersection controller unit. The controller evaluates the request and uses the RSU to send a reply to the vehicle. Read more about public transportation vehicle preference on a dedicated page. We also prepared a solution with foreign on-board computers.
• Speed optimization in front of an intersection – if an intersection is equipped with an RSU unit it can broadcast a signal plan of the controller. Based on this plan a vehicle can recommend to the driver a speed preventing pointless waiting at the red light.
  

  Pic. no.2 :States of two intersections as seen by a public transportation vehicle. Besides the current state, future state is broadcasted including the times of the red/green light. Speed can be adjusted accordingly to ensure passing through without stopping. The dark blue bands are lanes as broadcasted by RSU.

• Ensuring connections – each vehicle uses V2X to send its position, speed, direction,. Public transportation vehicles can also send information about their line, course, destination, delay and operator. Vehicle OBU receives this information and it can provide the EPIS computer with information about vehicles in the area. Using this information the on-board computer displays information about connections to the driver.
  

  Pic. no.3: A section of a map with vehicles in the area as they report via V2X. The advantage is that with V2X the driver can learn about a vehicle in the surroundings without seeing it directly (a possible alternative for LTE communication).

• Data for intelligent stops – an intelligent stop equipped with V2X can receive messages from vehicles in the area, thus display the estimated arrival time and stop displaying the vehicle when it departs.
• Information about exceptional traffic events – V2X can be used to send warning about exceptional traffic situations by using specific messages, for example about abrupt braking of a tram (brake activation), warning about slipping wheels of a vehicle in the front or about a driver that has exited a vehicle to throw a switch, etc.
  

  Pic. no.4: An example of a warning on a driver LCD terminal during an urgent passing of an ES vehicle. Simultaneously, the driver is informed by a sound signal. The information can be improved by adding the direction from which it is coming.

• Solution of exceptional situations – if there is an exceptional situation a dispatcher can send V2X messages (e.g. speed limit, redirection, …) in addition to the phonic connection with vehicles. They can be send from a mobile RSU or from a dispatching vehicle. They are displayed on an on-board computer.
• Warning for the driver against an imminent tram collision – thanks to V2X communicaton a vehicle “knows” about a vehicle in front of it and if the driver does not start decelerating in time a warning is displayed on the on-board computer. Deceleration information comes from a tachograph, a CAN busbar or an accelerometer. Read a detailed description of a test here.

Basic unit equipment

Our units UCU 5.0V  (V denotes a vehicle unit) are offered in various versions with various mechanical configuration and equipment for the purposes of public transportation. The typical UCU 5.0V unit equipment includes:

• V2X communication – supporting antenna diversity for better reception, or two-channel operation.
• Mobile internet connection – LTE – for connection with a central Back office server and for secure V2X communication certificate updates. Two independent modems possible.
• Position sensor – GNSS (GPS, Galileo and Glonass) – for accurate position and time
• Accelerometer and gyroscope for better position estimation and non-standard situation detection
• Wi-Fi access point – is also ready to provide Wi-Fi access to passengers. More about Wi-Fi here.
• The unit behaves as a router and can provide mobile internet connection to any other on-board informatics feature.

1 Gbit Ethernet is used to connect to the on-board computer. There is an option of equipping the unit with a second ethernet for connection to the vehicle board network (e.g. camera system). The following busbars can also be added to meet public transportation needs:

• RS-485, RS-232 – to connect to older vehicle technologies, e.g. older tachographs
• CAN – to read data about the drive of the vehicle – our unit supports the J1939 standard of utilization in buses and trucks. Thus it is possible to obtain information about speed, tire pressure, vehicle revs, consumption, …
• One-bit inputs – for information about other vehicle signals – detection of wheel slipping, doors, … as needed by individual customers.

Our units have a permission to be installed in road vehicles as well as in rail vehicles (we have a permission from the rail authority).

Mechanical configuration of UCU units

Because of frequent space restrictions in PT vehicles we offer the unit in three mechanical configurations (a more detailed description here):

• Compact for installation inside a vehicle – an external multi-antenna (2xV2X, 1xLTE and 1xGNSS). The unit is installed in the electronics case. Antenna cables are then brought to the unit. The advantages include simple configuration and easy connection of all other busbars (Ethernet, . . .). The disadvantage is the necessity of  bringing the antenna cables to it as they are quite thick.
• Compact for installation on the roof – an “all-in-one” unit type – electronics and antennas are all in one case that is installed on the roof. Ethernet and power supply have to be brought to the unit. The advantages include good signal, simple installation and good accessibility of the unit. The disadvantage can be difficult connectivity of other vehicle technologies – it is more difficult to bring cables (RS-485, …)..
• Divided version – one unit including all antennas is on the roof and it takes care of all wireless communication  (V2X, LTE, GNSS). This unit is connected to another unit by one cable. The other unit takes care of the connection to other vehicle technologies (Ethernet, power supply, …). This version combines the advantages of the other two versions – good signal, simple installation, good connectivity to vehicle busbars. The disadvantage is worse service – servicing two units instead of one.

Data processing

The units can contain map data which ensures for example correct generation of warning messages. It is also possible to localize vehicles directly for their route and mainly for rails notwithstanding the not completely accurate position from GNSS. The OBU unit can also work directly with measured speed obtained from the CAN busbar or from the tachograph.

We have functional communication with tachographs from the Mesit company – version TT32 and TT62. We can also prepare a CAN busbar with the J1939 norm for buses. We also offer a busbar separator along with the CAN busbar to ensure secure connection.