signal table structure

Each unique signal signal is associated to a unique node in the network and has associated to it a number of different phasing schemes times for different times of the day, as described on Signal_Nested_Records.

Each signal is also a part of a group of signals (NEED DESCRIPTION OF PURPOSE HERE).

For the time being, the field type is always equal to “TIMED” and the offset is always 0.

An index on nodes enforces the existence of a single signal per intersection

Table Structure

Field	Type	NULL allowed	Default Value	Foreign key	Description
signal*	INTEGER	NO			signal identifier
group	INTEGER	NO	0		not used by POLARIS
times	INTEGER	YES			number of timing records for this signal
nodes	INTEGER	NO	-1	Node(nodes)	actual node (Node table) that the signal infomation refers to
type	TEXT	NO	‘’		type (TIMED, ACTUATED). Generally TIMED is used
offset	INTEGER	NO	0		not used by POLARIS
osm_id	INTEGER	YES			the node in open street maps of the traffic signal

(* - Primary key)

The SQL statement for table and index creation is below.

create TABLE IF NOT EXISTS "Signal" (
    "signal" INTEGER NOT NULL PRIMARY KEY,
    "group"  INTEGER NOT NULL DEFAULT 0,
    "times"  INTEGER,
    "nodes"  INTEGER NOT NULL DEFAULT -1,
    "type"   TEXT    NOT NULL DEFAULT '',
    "offset" INTEGER NOT NULL DEFAULT 0,
    "osm_id" INTEGER,

    CONSTRAINT "nodes_fk" FOREIGN KEY("nodes") REFERENCES "Node"("node") DEFERRABLE INITIALLY DEFERRED
);

CREATE UNIQUE INDEX IF NOT EXISTS "Signal_signal_i" ON "Signal" ("signal");

CREATE UNIQUE INDEX IF NOT EXISTS "Signal_node_i" ON "Signal" ("nodes");