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# link types table structure

The link_types table holds information about the available link types in the network.

The link_type field corresponds to the link type, and it is the table’s primary key

The link_type_id field presents the identification of the link type

The description field holds the description of the link type

The lanes field presents the number or lanes for the link type

The lane_capacity field presents the number of lanes for the link type

The speed field holds information about the speed in the link type Attributes follow

Field | Type | NULL allowed | Default Value
--- | --- | --- | ---
link_type* | VARCHAR | NO |
link_type_id | VARCHAR | NO |
description | VARCHAR | YES |
lanes | NUMERIC | YES |
lane_capacity | NUMERIC | YES |
speed | NUMERIC | YES |

(* - Primary key)

The SQL statement for table and index creation is below.

    CREATE TABLE  if not exists link_types (link_type     VARCHAR UNIQUE NOT NULL PRIMARY KEY,
                                            link_type_id  VARCHAR UNIQUE NOT NULL,
                                            description   VARCHAR,
                                            lanes         NUMERIC,
                                            lane_capacity NUMERIC,
                                            speed         NUMERIC
                                            CHECK(LENGTH(link_type_id) == 1));

    INSERT INTO 'link_types' (link_type, link_type_id, description, lanes, lane_capacity) VALUES('centroid_connector', 'z', 'VIRTUAL centroid connectors only', 10, 10000);

    INSERT INTO 'link_types' (link_type, link_type_id, description, lanes, lane_capacity) VALUES('default', 'y', 'Default general link type', 2, 900);

    INSERT INTO 'attributes_documentation' (name_table, attribute, description) VALUES('link_types','link_type', 'Link type name. E.g. arterial, or connector');
    INSERT INTO 'attributes_documentation' (name_table, attribute, description) VALUES('link_types','link_type_id', 'Single letter identifying the mode. E.g. a, for arterial');
    INSERT INTO 'attributes_documentation' (name_table, attribute, description) VALUES('link_types','description', 'Description of the same. E.g. Arterials are streets like AequilibraE Avenue');
    INSERT INTO 'attributes_documentation' (name_table, attribute, description) VALUES('link_types','lanes', 'Default number of lanes in each direction. E.g. 2');
    INSERT INTO 'attributes_documentation' (name_table, attribute, description) VALUES('link_types','lane_capacity', 'Default vehicle capacity per lane. E.g.  900');
    INSERT INTO 'attributes_documentation' (name_table, attribute, description) VALUES('link_types','speed', 'Free flow velocity in m/s');