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.

### Structure of compound object controlled links

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.

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