Traffic Lights

SUMO offers some possibilities to save states of traffic lights during the simulation, a feature mainly used to evaluate adaptive traffic light algorithms. We will now describe these outputs.

## TLS States

### Instantiating within the Simulation

To enable writing tls state information you have to add the following definition into one of your additional-files:

`<timedEvent type="SaveTLSStates" source="<TLS_ID>" dest="<OUTPUT_FILE>"/>`

The attributes have herein the following meanings:

Attribute Name | Value Type | Description
--- | --- | ---
type | enum (string) | type of the event trigger; always "SaveTLSStates" herein.
source | referenced tls id | The id of the traffic light which state shall be written.
dest | file name | The file to save the state into.
saveDetectors | bool | Whether detector states shall be saved
saveConditions | bool | Whether condition states shall be saved

### Generated Output

The output looks like this:

    <tlsStates>
       <tlsState time="<SIM_STEP>" id="<TLS_ID>" programID="<TLS_SUBID>" phase="<PHASE_INDEX>" state="<STATE>"/>
       ... further states ...
    </tlsStates>

The state is saved in each simulation step. The state itself is coded as a list of the characters 'G', 'Y', and 'R', standing for "green", "yellow", and "red", respectively, see Simulation/Traffic Lights. Each character describes a link controlled by the traffic light. Only the state of the current program is saved (see also "Adding new Programs"). The attributes have the following meaning:

Name | Type | Description
--- | --- | ---
time | (simulation) seconds | The simulation time this entry was generated for
id | id | The id of the tls that is responsible for the link.
programID | id | The sub-id of the tls that is (currently) responsible for the link.
phase | uint | The index of the reported phase within the program
state | id | The current state

### Optional Output

If the the attributes 'saveDetectors' or 'saveConditions' are set, additional attributes are written to the output. These attributes are only written for traffic lights controlled by detectors and for traffic lights with custom switching rules respectively.

Element | Name | Type | Description
--- | --- | --- | ---
tlsStates | detectors | list (strings) | The ids of all detectors that are controlling this traffic light
tlsState | detectors | list (int) | The activation state of all detectors that are controlling this traffic light
tlsStates | conditions | list (strings) | The ids of all (visible) conditions that are controlling this traffic light
tlsState | conditions | list (int) | The value of all (visible) conditions that are controlling this traffic light

## TLS Switches

### Instantiating within the Simulation

This output contains information about the green light phases of links (lane-to-lane connections). Each green light phase is describes by its begin, end and duration. An entry is written into the file as soon a green phase of a link ends. To enable writing tls switch information you have to add the following definition into one of your additional-files:

`<timedEvent type="SaveTLSSwitchTimes" source="<TLS_ID>" dest="<OUTPUT_FILE>"/>`

The attributes have herein the following meanings:

Attribute Name | Value Type | Description
--- | --- | ---
type | enum (string) | type of the event trigger; always "SaveTLSSwitches" herein.
source | referenced tls id | The id of the traffic light which state shall be written.
dest | file name | The file to save the state into.

### Generated Output

The output looks like this:

    <tlsSwitches>
       <tlsSwitch tls="<TLS_ID>" programID="<TLS_SUB_ID>" \
          fromLane="<LINKS_SOURCE_LANE>" toLane="<LINK_DESTINATION_LANE>" \
          begin="<BEGIN_OF_GREEN_PHASE>" end="<END_OF_GREEN_PHASE>" \
          duration="<DURATION_OF_GREEN_PHASE>"/>
       ... further switch points ...
    </tlsSwitches>

Each entry is written into a single line. The values have the following meanings:

Name | Type | Description
--- | --- | ---
tls | id | The id of the tls that is responsible for the link.
programID | id | The sub-id of the tls that is (currently) responsible for the link.
fromLane | id | The id of the lane the link starts at.
toLane | id | The id of the lane the link ends at.
begin | (simulation) seconds | Begin of this link's last green phase.
end | (simulation) seconds | End of this link's last green phase.
duration | (simulation) seconds | Duration of this link's last green phase.

## TLS Switch States

### Instantiating within the Simulation

This output saves tls-states as the TLS States - output does but not every second but only at times the phases or the program (see also "Adding new Programs") change. The output is instantiated by adding the following definition into one of your additional-files:

`<timedEvent type="SaveTLSSwitchStates" source="<TLS_ID>" dest="<OUTPUT_FILE>"/>`

The attributes have herein the following meanings:

Attribute Name | Value Type | Description
--- | --- | ---
type | enum (string) | type of the event trigger; always "SaveTLSSwitchStates" herein.
source | referenced tls id | The id of the traffic light which state shall be written.
dest | file name | The file to save the state into.

### Generated Output

The output looks like this:

    <tlsStates>
       <tlsState time="<SIM_STEP>" id="<TLS_ID>" programID="<TLS_SUBID>" phase="<PHASE_INDEX>" state="<STATE>"/>
       ... further states ...
    </tlsStates>

Each entry is written into a single line. The values have the same meaning as those in the SaveTLSStates-output.

## TLS Programs

### Instantiating within the Simulation

To enable writing tls state information you have to add the following definition into one of your additional-files:

`<timedEvent type="SaveTLSProgram" source="<TLS_ID>" dest="<OUTPUT_FILE>"/>`

The attributes have herein the following meanings:

Attribute Name | Value Type | Description
--- | --- | ---
type | enum (string) | type of the event trigger; always "SaveTLSStates" herein.
source | referenced tls id | The id of the traffic light which state shall be written.
dest | file name | The file to save the state into.

### Generated Output

The output is a loadable tlLogic element that records the complete state sequence of a traffic light:

    <tlsStates>
       <tlLogic id="<TLS_ID>" programID="<TLS_SUBID>" type="static/>
          <phase state="..." duration="..."
          ...
       </tlLogic>
    </tlsStates>

A new phase is saved whenever the state changes. A new tlLogic is written whenever the programID changes.

## Coupled Lane Area Detectors

### Instantiating within the Simulation

It is possible to add E2-detectors which are coupled to a traffic light. Then, the tls is used to determine the intervals (aggregation) time instead of giving a fixed aggregation time. In this case, output will be generated every time the traffic light switches. To use this feature set attribute `tl="<TL_ID>"` to the desired traffic light id instead of attribute `<period>`:

`<e2Detector id="<ID>" lane="<LANE_ID>" pos="<POSITION_ON_LANE>" length="<DETECTOR_LENGTH>" tl="<TL_ID>" file="<OUTPUT_FILE>" [timeThreshold="<FLOAT>"] [speedThreshold="<FLOAT>"] [jamThreshold="<FLOAT>"]/>`

A further feature allows you to collect measures only for the time the light turns red for a certain link (connection between the incoming and the outgoing lane). This allows measuring the maximum jam length in front of a red traffic light for this link. To enable this, one has to add the name of the following lane: `to="<LANE_ID>"` to the list of attributes. The incoming lane is already given by the "`lane`"-attribute.

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