ISO 22951:2009

INTERNATIONAL ISO
STANDARD 22951
First edition
2009-01-15

Data dictionary and message sets for
preemption and prioritization signal
systems for emergency and public
transport vehicles (PRESTO)
Dictionnaire de données et ensembles de messages pour la préemption
et la priorisation des systèmes de signaux pour les véhicules d'urgence
et de transport public (PRESTO)




Reference number
ISO 22951:2009(E)
©
ISO 2009

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ISO 22951:2009(E)
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ISO 22951:2009(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Normative references . 2
3 Terms and definitions. 2
4 Symbols and abbreviated terms . 3
5 Data dictionary and message sets for PRESTO. 3
5.1 Data dictionary. 3
5.2 Message sets. 4
Annex A (informative) The concept of PRESTO. 5
Annex B (informative) PRESTO architecture. 7
Annex C (normative) PRESTO requirements list . 17
Annex D (informative) Needs for standardization. 43
Annex E (informative) Background of constructing PRESTO system architecture (SA) . 44
Annex F (informative) Practical examples of PRESTO. 47
Bibliography . 50

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ISO 22951:2009(E)
Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 22951 was prepared by Technical Committee ISO/TC 204, Intelligent transport systems.

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ISO 22951:2009(E)
Introduction
It is very important that police cars, fire engines, and other emergency vehicles arrive at the scene to which
they are dispatched as soon as possible in order to improve crime prevention rate, lifesaving rate etc.
Therefore, various countries are using, or developing, preemption signal-systems to support the smooth
travelling of such vehicles. In addition, some countries use these priority signal-controls for buses and other
public transport vehicles to provide punctual and more convenient service. This International Standard
standardizes communication messages in these preemption signal-systems for emergency and public
transport vehicles, aiming to promote system introduction through developing a common infrastructure.

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INTERNATIONAL STANDARD ISO 22951:2009(E)

Data dictionary and message sets for preemption and
prioritization signal systems for emergency and public
transport vehicles (PRESTO)
1 Scope
This International Standard relates to systems that use priority signal control functions to help emergency
vehicles operate. This type of system, as shown in Figure 1, is composed of a traffic management centre,
in-vehicle units, roadside communication units, and roadside units. Public transport vehicles such as buses
are also targeted to receive priority signal control service.
The scope of standardization includes message sets and data dictionary related to the communications
as follows:
⎯ between a roadside communication unit and each in-vehicle unit,
⎯ between a roadside communication unit and other roadside units,
⎯ between in-vehicle units and roadside units.
This International Standard concerns only information related to priority signal control and does not deal with
information provision such as that of the situations at scenes. Since it is necessary to handle public transport
vehicles in accordance with the conditions of individual cities and regions, the section in the messages and
the data dictionary that are concerned with priority signal control for the vehicles are treated as an option.
Furthermore, the standardization does not depend on the type of communication medium used.

Figure 1 —Scope of standardization work
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ISO 22951:2009(E)
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 14817, Transport information and control systems — Requirements for an ITS/TICS central Data Registry
and ITS/TICS Data Dictionaries
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 14817 and the following apply.
3.1
antenna
roadside equipment that communicates with the roadside units such as signal controllers and the in-vehicle
units using radio signals
3.2
beacon
roadside equipment that communicates with the roadside units such as the signal controllers and the
in-vehicle units
3.3
data dictionary
listing of data elements (and their characteristics) that meets the information and functional needs of a system
3.4
data element
atomic element of information
NOTE A data element is a syntactically formal representation of some information of interest (such as a fact,
proposition, observation, etc.) about some entity of interest (e.g. a person, place, process, property, object, concept,
association, state, event).
3.5
in-vehicle unit
in-vehicle equipment that transmits/receives information to/from the roadside communication units and, in
some cases, outputs information, for example, on its screen
3.6
message sets
set of basic messages that are normally used in business-oriented applications
3.7
roadside communication unit
roadside equipment that communicates with the in-vehicle units and the roadside units, e.g. beacons and
antennas
3.8
roadside unit
roadside equipment that controls signals and provides information, e.g. the signal controllers and the
information board controllers
3.9
signal controller
roadside equipment that controls the lighting timings of traffic lights
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ISO 22951:2009(E)
3.10
traffic management centre
central system that controls the functions of traffic data collection, signal control, and information service
based on collected data, etc.
3.11
vehicle ID
identification number used for the identification of emergency and/or public transport vehicles
4 Symbols and abbreviated terms
PRESTO data dictionary and message sets for preemption and prioritization signal systems for emergency
and public transport vehicles
5 Data dictionary and message sets for PRESTO
Tables 1 and 2 give the list of data dictionary and message sets within the scope of the standardization, in-line
with the data concept specified in ISO 14817. Further details are given in Annex C.
5.1 Data dictionary
Table 1 — Data dictionary within the scope of the standardization
Data concept ASN.1 object identifier ASN.1 name Descriptive name
type
Data element {iso standard presto concepts dec 1 10} PSC.authority-classification PSC.authorityClassification
concept
Data element {iso standard presto concepts de 1 20} PSC.vehicle-code PSC.vehicleCode
{iso standard presto concepts de 1 30} PSC-transport-mode PSC.transportMode
{iso standard presto concepts de 1 40} PSC-priority-signal-request- PSC.prioritySignalRequestFlag
flag
{iso standard presto concepts de 1 50} PSC-request-intersection id PSCrequestIntersectionID
{iso standard presto concepts de 1 60} PSC-direction-at-intersection PSC.directionAtIntersection
{iso standard presto concepts de 1 70} PSC-spot-id PSC.spotID
{iso standard presto concepts de 1 80} PSC-spot-passing-time PSC.spotPassingTime
{iso standard presto concepts de 1 90} PSC-vehicle-speed PSC.vehicleSpeed
{iso standard presto concepts de 1 100} PSC-vehicle-acceleration PSC.vehicleAcceleration
{iso standard presto concepts de 1 110} PSC-travel-distance PSC.travelDistance
{iso standard presto concepts de 1 120} PSC-transmission-time PSC.transmissionTime
Data frame {iso standard presto concepts df 1 130} PscVehicleID PscVehicleID:frame
{iso standard presto concepts df 1 140} PscPrioritySignalRequest PscPrioritySignalRequest:frame
{iso standard presto concepts df 1 150} PscVehicleCurrentLocation PscVehicleCurrentLocation:frame
{iso standard presto concepts df 1 160} PsctravelInformation PsctravelInformation:frame
{iso standard presto concepts df 1 170} PscSpotLocation PscSpotLocation:frame
{iso standard presto concepts df 1 180} PscSpotPassingPoint PscSpotPassingPoint:frame
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ISO 22951:2009(E)
5.2 Message sets
Table 2 — Messages sets within the scope of the standardization
Data concept ASN.1 object identifier ASN.1 name Descriptive name
type
Message {iso standard presto concepts PscVehicleInformation PscVehicleInformation:message
mes 1 190}
{iso standard presto concepts PscVehicleData PscVehicleData:message
mes 1 200}
{iso standard pi 11} PiSchedAdherenceOffSched PiSchedAdherenceOffSched:message

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ISO 22951:2009(E)
Annex A
(informative)

The concept of PRESTO
A.1 Purpose
PRESTO allows emergency vehicles such as police cars, fire engines and so forth to speedily and accurately
respond to emergencies by carrying out traffic signal control with the highest priority and guiding optimal
routes for these vehicles. In addition, this system draws the attention of general vehicles and pedestrians by
indicating the approach of emergency vehicles on message boards. This system carries out priority signal
control for public transport vehicles such as buses and trams. By providing travelling support to emergency
vehicles and public transport vehicles in this way, the system intends to achieve the realization of the following
effects.
a) Reduction in the response time of emergency vehicles:
⎯ early resolution of accidents and improvement of arrest rates;
⎯ support for speedy rescue activity and improvement of lifesaving rates.
b) Reduction of the number of traffic accidents associated with en-route emergency vehicles.
c) Improvement of convenience of public transport vehicles such as buses and trams by securing the
regular time operation of them.
A.2 Basic function
This system has the functions of
⎯ priority signal control,
⎯ route guidance, and
⎯ safety support.
The priority signal control function includes macro control function and micro control function.
The macro control function transmits signal parameters beforehand, for example, giving maximum green time
in the direction of emergency vehicles and public transport vehicles to the group of traffic signals at
intersections from the traffic management centre, so it is possible to reduce traffic jams and lines of vehicles
waiting for a green signal, which are hindrance factors to a priority traffic route.
The micro control function extends the green time or reduces the red time by having the vehicle sensor detect
approaching emergency vehicles and public transport vehicles in order to let those vehicles pass through the
green light.
The route guidance function effectively supports an early arrival of emergency vehicles at the scene of an
accident by guiding the emergency vehicles from their current position to the scene of the accident through
the recommended route. The macro control function, as explained above, links to the route guidance function
and minimizes disadvantages suffered by general vehicles and pedestrians.
The safety support function draws attention of the general vehicles and pedestrians to the approaching
emergency vehicle via the message board.
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ISO 22951:2009(E)
Furthermore, the priority signal control function and safety support function carry out the above functions by

1) 2)
managing the signal control computer and information-board control computer from the traffic management
centre that takes the role of traffic control for general vehicles.
As stated above, the system covers public transport vehicles, including buses and trams (LRTs), in its priority
signal control. This system will be put into service in road sections where it is expected to enhance the
punctual operation of such vehicles and reduce adverse impact on general vehicles.

1) One of the central functions that controls the signal controllers through the transmission of signal parameters, etc.
2) Roadside equipment that controls the information boards that display traffic information through their instructions.
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ISO 22951:2009(E)
Annex B
(informative)

PRESTO architecture
B.1 Overview of PRESTO user services
A requirement analysis based on the concepts given in Annex A was conducted and used to define PRESTO
user services shown in Table B.1. PRESTO user services are systematized by referring to user subservices in
the system architecture for ITS in Japan, which are described in Annex E.
Table B.1 — PRESTO user services
Specific user subservices Description
Provide signal priority to bus and tram
To assist the improvement of the functional efficiency of public
transportation and the management of its safe and smooth operation,
implements a signal control system. The system detects information sent
from public transport vehicles that includes notification of their approach
to signalized intersections, lane change sections, their proceeding into
main roads from bus bays, etc. and control signals to prioritize their
passage.
Guide emergency vehicles along the When an accident, etc. occurs, collects in real-time information regarding
optimum routes the current road traffic conditions including traffic backup, the effects of
road work, etc. and guides emergency vehicles to their destinations to
enable them to mount their rescue operations quickly and appropriately.
Control traffic signals for priority To provide support for the quick movement of emergency vehicles and
guidance of emergency vehicles improve their safety when they are mobilized in connection with an
accident, etc. that have occurred, controls traffic signals appropriately so
as to enable them, when they approach intersections, to pass through
with priority and safely.
Inform vehicles of approaching When an accident, etc. occurs, provides the drivers of vehicles ahead
emergency vehicles with information about the approach of emergency vehicles so as to
provide support for the quick passage of emergency vehicles and assure
their safe passage.
Manage emergency and public transport To provide support for quick and appropriate rescue operations when an
vehicle operations accident, etc. occurs, collects in real-time information, etc. regarding the
locations of emergency and public transport vehicles and proceeds to
appropriate vehicle allocation taking into account the status of the site of
the accident, etc., and the present locations of emergency and public
transport vehicles.
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ISO 22951:2009(E)
B.2 Definition of functions and messages
The necessary functions and messages for each PRESTO user service have been analysed and extracted.
B.2.1 Function name
Function name is the name of the function.
B.2.2 Common function
Common function is a common number given to a group of elements that is categorized by function in several
user services.
B.2.3 Message name
Message name is the name of the messages received and transmitted by the functional elements.
B.2.4 Common message
Common message is a common number given to each message in several functional elements.
B.2.5 Definition of words in messages
a) Information – information received and transmitted between this system and “object” (vehicles and
information sources)
b) Data – data received and transmitted in this system.
c) Status – information received and transmitted between this system and the “object” (vehicles and
information sources). The format is not specified.
d) Control – the practical order of control action based on control parameters.
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ISO 22951:2009(E)
B.3 Descriptions of functions
Table B.2 — PRESTO functions
No. Function Description Corresponding physical device
F01 Roadway&Traffic_Status_ It gathers the PrtRoadwayStatus and the Traffic management centre /
Collection PrtTrafficStatus. emergency vehicle management
centre / public vehicle
management centre
F02 Scene_Information_Collect It gathers the PrtSceneStatus and notifies it in Emergency vehicle management
ion&Call response to the requests from emergency centre
vehicles.
F03 Traffic_Prediction It predicts the future traffic conditions from the Traffic management centre /
PrtRoadway&TrafficStatusData and creates the emergency vehicle management
PrtPredictedTrafficData. centre / public vehicle
management centre
F04 Destination_Identification It identifies the destination from Emergency vehicle management
PrtIncidentInformation. centre
F05 Vehicle_Identification It authenticates whether or not the emergency Emergency vehicle management
vehicles are subject to priority signal service centre / public vehicle
from their PscVehicleData. This PscVehicleData management centre / roadside
includes the priority signal request, the vehicle communication unit (beacon,
ID, the current location, the passage (or the antenna) / roadside unit (signal
receiver ID), the vehicle travel information controller)
(speed, acceleration, mileage, GPS information,
etc.), the destination, and the route information.
It also tries to find the most probable current
location based on the information included in the
PscVehicleData, and then creates the
PrtVehicleLocationData. This function may
convert the passage, the receiver ID, or the
vehicle travel information into the location
information depending on the system. If the
vehicles are identified as subject to priority signal
service with this function, it will send the
PrtVehicleLocationData to the
Priority_Verification, the Route_Calculation, the
Micro_Priority_Control_Adjudication, the
Macro_Priority_Control_Adjudication, and the
Vehicle_Approaching_Position_Adjudication.
F06 Route_Calculation Under the traffic conditions indicated by the Emergency vehicle management
PrtRoadway&TrafficStatusData and the centre
PrtPredictedTrafficData, it will calculate the
PrtRouteData of the emergency vehicle’s current
location to the destination, and send the result to
the Each Route_Verification.
F07 EachRoute_Verification Under the situation where a number of Traffic management centre
emergency-vehicle-routes coexist, it will adjust
the route for each emergency vehicle by
following the Priority Level, then create the
PrtRecommendedRouteData.
F08 Route_Information_Provisi It provides emergency vehicles with Traffic management centre
on PrtRecommendedRouteData.
F09 Roadway&Traffic_Informat It gives the Emergency vehicle management
ion_Call PrtRoadway&TrafficStatusInformation in centre / roadside unit (beacon)
response to the requests from emergency
vehicles.
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ISO 22951:2009(E)
Table B.2 (continued)
No. Function Description Corresponding physical device
F10 Micro_Priority_Signal_Con Following the instructions of the Traffic Management Centre /
trol_Pattern_Generation Micro_Priority_Signal_Adjudication, it generates Roadside Unit (Signal Controller)
the PrtMicroControlData based on the general
signal data, and then transmits it to the
Signal_Control.
F11 Signal_Control It controls the Traffic_Signal and turns on the Roadside unit (signal Controller)
light
F12 Vehicle_Information_Rece After receiving the PscVehicleInformation from Traffic management centre /
ption emergency vehicles and carrying out the emergency vehicle management
required processing, it creates PscVehicleData centre / roadside communication
and sends it to the Vehicle_Identification. This unit (beacon, antenna)
PscVehicleInformation and PscVehicleData
include the priority signal request, the vehicle ID,
the location, the passage (or the receiver ID), the
vehicle travel information (speed, acceleration,
mileage, GPS information, etc.), the route, and
the destination. This function may configure the
receiver ID instead of the passage point
depending on the system. Likewise, for public
vehicles, it also receives the
PscVehicleInformation and sends the
PscVehicleData to the
PublicVehicle_Identification. In addition, it
receives the PiSchedAdherenceOffSched that
includes the delay from the running schedule or
the “planned” schedule, and then sends it to the
PublicVehicle_Identification.
F13 Vehicle_Approaching_Posi It identifies the approaching emergency vehicles Traffic management centre /
tion_Adjudication from the PrtVehicleLocatioinData. roadside unit (information board
controller)
F14 Vehicle_Approaching_Infor Notify the PrtWarningInformation, which warns Traffic management centre /
mation_Warning the approaching emergency vehicles, to the roadside unit (information board
warning boards, the information boards, and controller)
general vehicles.
F15 Vehicle_Operating_Status By analyzing the PrtRecommendedRouteData, Traffic management centre
_Call the PRtVehicleLocationData and
PiSchedAdherenceOffSched, it creates the route
information, the management information, and
the mileage trace information, of the emergency
vehicles and the public vehicles. Such
information will be sent to the emergency vehicle
management centre or the public vehicle
management centre upon their requests.
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ISO 22951:2009(E)
Table B.2 (continued)
No. Function Description Corresponding Physical Device
F16 Priority_Verification For emergency vehicles certified as subject to Traffic management centre /
priority signal service, it decides the priority level roadside unit (signal controller)
and creates the PrtPriorityLevelData based on
information included in PrtVehicleLocationData:
the vehicle ID, the current location, and the
estimated arrival time. For public vehicles, it will
also take into account any running schedule
delay, when creating the priority level. To
calculate the delay extent, it could rely on the
PrtVehicleLocationData, the running schedule
included in PiSchedAdherenceOffSched (or the
information sent by the public vehicle
management centre), delay information included
in the PiSchedAdherenceOffSched, or notice of
delay given by the public transport vehicle
management centre (through the traffic
management centre when F16 belongs to the
roadside unit). The priority level will be given
considering both emergency vehicles and public
vehicles in common. As well as notifying the
PrtPriorityLevelData to the
EachRoute_Verification, by notifying it to the
Micro_Priority_Control_Adjudication and
Macro_Priority_Control_Adjudication, it requests
the priority signal service.
F17 PublicVehicle_Identification It authenticates whether or not the public Traffic management centre /
vehicles are subject to priority signal service public vehicle management
from their PscVehicle_Data and centre / roadside communication
PiSchedAdherenceOffSched. This unit (beacon, antenna) / roadside
PscVehicleData includes the priority signal unit (signal controller)
request, the vehicle ID, the current location, the
passage (or the receiver ID), the vehicle travel
information (speed, acceleration, mileage, GPS
information, etc.), the destination, and the route
information. It also tries to find the most probable
current location based on the information
included in the PscVehicleData, and then
creates the PrtVehicleLocationData. This
function may convert the passage, the receiver
ID, or the vehicle travel information into the
location information depending on the system. If
the vehicles are identified as subject to priority
signal service with this function, it will send the
PrtVehicleLocationData to the
Priority_Verification, the
Micro_Priority_Control_Adjudication, the
Macro_Priority_Control_Adjudication, and the
Vehicle_Approaching_Position_Adjudication.
F18 Macro_Priority_Signal_Co Following the instruction of Traffic management centre
ntrol_Pattern_Generation Macro_Priority_Signal_Control_Pattern_Adjudica
tion, it generates the PrtMacroControlData for
the use of macro-priority-control based on the
general signal-control data, and transmits it to
the Signal_Control.
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ISO 22951:2009(E)
Table B.2 (continued)
No. Function Description Corresponding physical device
F19 Micro_Priority_Signal_Con It extracts the information of the intersection Traffic management centre /
trol_Adjudication point, the moving direction at the intersection roadside unit (signal controller)
and the arrival time at the specified intersection
from the PrtVehicleLocationData of the
...