Traffic Lights Value Retrieval

Command 0xa2: Get Traffic Lights Variable#

ubyte string
Variable Traffic Lights ID

Asks for the value of a certain variable of the named traffic light. The value returned is the state of the asked variable/value within the last simulation step. The following variable values can be retrieved, the type of the return value is also shown in the table.

Overview Retrievable Traffic Lights Variables

Variable ValueType Description Python Method
id list (0x00) stringList Returns a list of ids of all traffic lights within the scenario (the given Traffic Lights ID is ignored) getIDList
count (0x01) int Returns the number of traffic lights within the scenario (the given Traffic Lights ID is ignored) getIDCount
state (light/priority tuple) (0x20) string Returns the named tl's state as a tuple of light definitions from rRgGyYoO, for red, green, yellow, off, where lower case letters mean that the stream has to decelerate getRedYellowGreenState
default current phase duration (0x24) double Returns the default total duration of the currently active phase in seconds; To obtain the remaining duration use (getNextSwitch() - simulation.getTime()); to obtain the spent duration subtract the remaining from the total duration getPhaseDuration
controlled lanes (0x26) stringList Returns the list of lanes which are controlled by the named traffic light. Returns at least one entry for every element of the phase state (signal index)(1)(2). getControlledLanes
controlled links (0x27) compound object Returns the links controlled by the traffic light, the index in the returned list corresponds to the tls link index of the connection. Each index maps to a list of link objects that share the same link index. Each link object is described by giving the incoming, outgoing, and via lane. getControlledLinks
current phase (0x28) int Returns the index of the current phase in the current program getPhase
current program (0x29) string Returns the id of the current program getProgram
complete definition (light/priority tuple) (0x2b) compound object Returns the complete traffic light program, structure described under data types getCompleteRedYellowGreenDefinition
assumed time of next switch (0x2d) double Returns the assumed time (in seconds) at which the tls changes the phase. Please note that the time to switch is not relative to current simulation step (the result returned by the query will be absolute time, counting from simulation start); to obtain relative time, one needs to subtract current simulation time from the result returned by this query. Please also note that the time may vary in the case of actuated/adaptive traffic lights getNextSwitch
blocking vehicles (0x25) stringList Returns the ids of vehicles that occupy the subsequent rail signal block getBlockingVehicles
rival vehicles (0x30) stringList Returns the ids of vehicles that are approaching the same rail signal block getRivalVehicles
priority vehicles (0x31) stringList Returns the ids of vehicles that are approaching the same rail signal block with higher priority getPriorityVehicles

Please note:

  1. Each lane may be the start of multiple links (connections across the intersection). Thus a lane may occur multiple times in the output

Response 0xb2: Traffic Lights Variable#

ubyte string ubyte <return_type>
Variable Traffic Light ID Return type of the variable <RETURN_VALUE>

The respond to a "Command Get Traffic Lights Variable".

Structure of compound object traffic light program (both 0x25 and 0x2b)#

If you request a complete traffic light program, the compound object is structured as following. Attention, each part is preceded by a byte which represents its data type, except "length".

integer type + integer logic ... logic
Length Number of logics logic 1 ... logic n

where logic is described by:

type + string type + integer type + compound type + integer type + integer phase ... phase
SubID Type SubParameter Current phase index Number of phases Phase 1 ... Phase n

Type and SubParameter aren't currently implemented therefore they are 0.

where phase is described by:

type + double type + double type + double type + string
Duration (in seconds) MinDuration (in seconds) MaxDuration (in seconds) Phase definition

MinDuration and MaxDuration are only relevant in the context of actuated traffic lights. The phase definition differs for 0x25 and 0x2b. The first (0x25) contains the old, deprecated definition which uses three strings that describe the tl's state, the first green y/n, the second for brake y/n, the third for yellow y/n. The second (0x2b) contains a single string representing the lights. Note, that the first (0x25) is also reversed.

If you request the list of links, the compound object is structured as following. Attention, each part is preceded by a byte which represents its data type, except "length".

integer controlled links ... controlled links
Length (number of signals) links controlled by signal 0 ... links controlled by signal n-1

Controlled links:

int stringlist ... stringlist
number of controlled links link 0 ... link n-1

Each link is described by a string list with three entries: the lane which is incoming into the junction, the lane which is outgoing from the junction, and the lane across the junction (junction-internal). Empty strings indicate missing lanes.

The method basically returns a list of lists of 3-tuples. The outer list has a length that corresponds to the length of the 'state' attribute of each phase. Each inner list (at position i of the outer list) describes the connections that are controlled by the state at index i.

By default, each index of the state controls exactly one connection so the inner lists all have length 1. However, the inner lists may be longer if signal-groups are used to simplify the 'state' attribute.

Getting Traffic light parameters (0x7e)#

Traffic lights support retrieval of additional parameters using the generic parameter retrieval call.

key return value type (expressed as string) supported by tlType description
cycleTime double (s) static, actuated, delay_based default cycle duration (has no effect for static tls)
cycleSecond double (s) static, actuated, delay_based time within cycle
offset double (s) static, actuated, delay_based offset for cycle start relative to simulation start
coordinated bool static, actuated, delay_based whether time in cycle is computed relative to simulation time
max-gap double (s) actuated detector time-out for abandoning phase
show-detectors bool actuated show/hide detectors in view
inactive-threshold double (s) actuated time-out for switching to an unserved phase when running with the default phase-skipping logic
condition.CONDITION_ID double actuated retrieve current value of custom switching condition with id = CONDITION_ID.