Road Network

Table of Contents

CSV / Parquet representation

CSV / Parquet representation

In METROPOLIS2, a road network is composed of a collection of edges and a collection of vehicle types. A road network is thus represented by two CSV or Parquet files:

edges.parquet (or edges.csv)
vehicles.parquet (or vehicles.csv)

Edges

Column	Data type	Conditions	Constraints	Description
`edge_id`	`Integer`	Mandatory	No duplicate value, no negative value	Identifier of the edge (used in some input files and used in the output).
`source`	`Integer`	Mandatory	No negative value	Identifier of the source node of the edge.
`target`	`Integer`	Mandatory	No negative value, different from `source`	Identifier of the target node of the edge.
`speed`	`Float`	Mandatory	Positive number	The base speed on the edge when there is no congestion, in meters per second.
`length`	`Float`	Mandatory	Positive number	The length of the edge, from source node to target node, in meters.
`lanes`	`Float`	Optional	Positive number	The number of lanes on the edge (for this edge’s direction). The default value is 1.
`speed_density.type`	`String`	Optional	Possible values: `"FreeFlow"`, `"Bottleneck"`, `"ThreeRegimes"`	Type of speed-density function used to compute congested travel time. If `null`, the free-flow speed-density function is used.
`speed_density.capacity`	`Float`	Mandatory if `speed_density.type` is `"Bottleneck"`, ignored otherwise	Positive number	Capacity of the road’s bottleneck when using the bottleneck speed-density function. Value is expressed in meters of vehicle headway per second.
`speed_density.min_density`	`Float`	Mandatory if `speed_density.type` is `"ThreeRegimes"`, ignored othewise	Between `0.0` and `1.0`	Edge density below which the speed is equal to free-flow speed.
`speed_density.jam_density`	`Float`	Mandatory if `speed_density.type` is `"ThreeRegimes"`, ignored othewise	Between `0.0` and `1.0`, larger than `speed_density.min_density`	Edge density above which the speed is equal to `speed_density.jam_speed`.
`speed_density.jam_speed`	`Float`	Mandatory if `speed_density.type` is `"ThreeRegimes"`, ignored othewise	Positive number	Speed at which all the vehicles travel in case of traffic jam, in meters per second.
`speed_density.beta`	`Float`	Mandatory if `speed_density.type` is `"ThreeRegimes"`, ignored othewise	Positive number	Parameter to compute the speed in the intermediate congested case.
`bottleneck_flow`	`Float`	Optional	Positive number	Maximum incoming and outgoing flow of vehicles at the edge’s entry and exit bottlenecks, in PCE per second. In `null`, the incoming and outgoing flow capacities are assumed to be infinite.
`constant_travel_time`	`Float`	Optional	Positive number	Constant travel-time penalty for each vehicle traveling through the edge, in seconds. If `null`, there is no travel-time penalty.
`overtaking`	`Boolean`	Optional		If `true`, a vehicle that is pending at the end of the edge to enter its outgoing edge is not prevending the following vehicles to access their outgoing edges. Default value is `true`.

Vehicle types

Column	Data type	Conditions	Constraints	Description
`vehicle_id`	`Integer`	Mandatory	No duplicate value, no negative value	Identifier of the vehicle type
`headway`	`Float`	Mandatory	Non-negative value	Typical length, in meters, between two vehicles, from head to head.
`pce`	`Float`	Optional	Non-negative value	Passenger car equivalent of this vehicle type, used to compute bottleneck flows. Default value is 1.
`speed_function.type`	`String`	Optional	Possible values: `"Base"`, `"UpperBound"`, `"Multiplicator"`, `"Piecewise"`	Type of the function used to convert from the base edge speed to the vehicle-specific edge speed. If `null`, the base speed is used.
`speed_function.upper_bound`	`Float`	Mandatory if `speed_function.type` is `"UpperBound"`, ignored otherwise	Positive number	Maximum speed allowed for the vehicle type, in meters per second.
`speed_function.coef`	`Float`	Mandatory if `speed_function.type` is `"Multiplicator"`, ignored otherwise	Positive number	Multiplicator applied to the edge’s base speed to compute the vehicle-specific speed.
`speed_function.x`	`List` of `Float`	Mandatory if `speed_function.type` is `"Piecewise"`, ignored otherwise	Positive numbers in increasing order	Base speed values, in meters per second, for the piece-wise linear function.
`speed_function.y`	`List` of `Float`	Mandatory is `speed_function.type` is `"Piecewise"`, ignored otherwise	Positive numbers, same number of values as `speed_function.x`	Vehicle-specific speed values for the piece-wise linear function.
`allowed_edges`	`List` of `Integer`	Optional	Values must be existing `edge_id` in the `edges` file	Indices of the edges that this vehicle type is allowed to take. If `null`, all edges are allowed (unless specificed in `restricted_edges`).
`restricted_edges`	`List` of `Integer`	Optional	Values must be existing `edge_id` in the `edges` file	Indices of the edges that this vehicle type cannot take.

Additional constraints

There must be no edges with the same pair (source, target) (i.e., no parallel edges).