uxsim.Link¶

class uxsim.Link(W: World, name: str, start_node: Node | str, end_node: Node | str, length: float, free_flow_speed: float = 20, jam_density: float = 0.2, jam_density_per_lane: float | None = None, number_of_lanes: int = 1, merge_priority: float = 1, signal_group: list[int] = [0], capacity_out: float | None = None, capacity_in: float | None = None, eular_dx=None, attribute=None, user_attribute=None, user_function=None, auto_rename=False)[source]¶

Link in a network.

Create a link.

Parameters:

W (object) – The world to which the link belongs.
name (str | None) – The name of the link. If None, the name is automatically generated as “{start_node.name}-{end_node.name}”.
start_node (str | Node) – The name of the start node of the link.
end_node (str | Node) – The name of the end node of the link.
length (float) – The length of the link.
free_flow_speed (float, optional) – The free flow speed on the link, default is 20.
jam_density (float, optional) – The jam density on the link, default is 0.2. If jam_density_per_lane is specified, this value is ignored.
jam_density_per_lane (float, optional) – The jam density per lane on the link. If specified, it overrides the jam_density value.
number_of_lanes (int, optional) – The number of lanes on the link, default is 1.
merge_priority (float, optional) – The priority of the link when merging at the downstream node, default is 1.
signal_group (int or list, optional) – The signal group(s) to which the link belongs, default is 0. If signal_group is int, say 0, it becomes green if end_node.signal_phase is 0. If signal_group is list, say [0,1], it becomes green if the end_node.signal_phase is 0 or 1.
capacity_out (float, optional) – The capacity out of the link, default is calculated based on other parameters.
capacity_in (float, optional) – The capacity into the link, default is calculated based on other parameters.
eular_dx (float, optional) – The space aggregation size for link traffic state computation, default is 1/10 of link length or free flow distance per simulation step, whichever is larger.
attribute (any, optional) – Additional (meta) attributes defined by users.
user_attribute (any, optional) – Additional (meta) attributes defined by users. Same functionality to attribute, but with more understandable name.
user_function (func, optional) –
User-defined custom function that is automatically called when the timestep is incremented (more precisely, when update() is called). It takes only one argument: the Link object itself. Example: The following code prints the current number of vehicles on the link at each timestep. If user_function=None (default), no functions will be executed.
```
>>> def user_function(link):
>>>     print(len(link.vehicles))
>>> W = World(...)
>>> W.addLink("link", "node1", "node2, 1000, user_function=user_function)
>>> ... #define your scenario
>>> W.exec_simulation()
```
auto_rename (bool, optional) – Whether to automatically rename the link if the name is already used. Default is False (raise an exception).

speed¶

Average speed of traffic on the link.

Type:: float

density¶

Density of traffic on the link.

Type:: float

flow¶

Flow of traffic on the link.

Type:: float

num_vehicles¶

Number of vehicles on the link.

Type:: float

num_vehicles_queue¶

Number of slow vehicles (due to congestion) on the link.

Type:: float

free_flow_speed¶

Free flow speed of the link.

Type:: float

jam_density¶

Jam density of the link.

Type:: float

capacity_out¶

Capacity for outflow from the link.

Type:: float

capacity_in¶

Capacity for inflow to the link.

Type:: float

merge_priority¶

The priority of the link when merging at the downstream node.

Type:: float

__init__(W: World, name: str, start_node: Node | str, end_node: Node | str, length: float, free_flow_speed: float = 20, jam_density: float = 0.2, jam_density_per_lane: float | None = None, number_of_lanes: int = 1, merge_priority: float = 1, signal_group: list[int] = [0], capacity_out: float | None = None, capacity_in: float | None = None, eular_dx=None, attribute=None, user_attribute=None, user_function=None, auto_rename=False)[source]¶

Create a link.

Parameters:

W (object) – The world to which the link belongs.
name (str | None) – The name of the link. If None, the name is automatically generated as “{start_node.name}-{end_node.name}”.
start_node (str | Node) – The name of the start node of the link.
end_node (str | Node) – The name of the end node of the link.
length (float) – The length of the link.
free_flow_speed (float, optional) – The free flow speed on the link, default is 20.
jam_density (float, optional) – The jam density on the link, default is 0.2. If jam_density_per_lane is specified, this value is ignored.
jam_density_per_lane (float, optional) – The jam density per lane on the link. If specified, it overrides the jam_density value.
number_of_lanes (int, optional) – The number of lanes on the link, default is 1.
merge_priority (float, optional) – The priority of the link when merging at the downstream node, default is 1.
signal_group (int or list, optional) – The signal group(s) to which the link belongs, default is 0. If signal_group is int, say 0, it becomes green if end_node.signal_phase is 0. If signal_group is list, say [0,1], it becomes green if the end_node.signal_phase is 0 or 1.
capacity_out (float, optional) – The capacity out of the link, default is calculated based on other parameters.
capacity_in (float, optional) – The capacity into the link, default is calculated based on other parameters.
eular_dx (float, optional) – The space aggregation size for link traffic state computation, default is 1/10 of link length or free flow distance per simulation step, whichever is larger.
attribute (any, optional) – Additional (meta) attributes defined by users.
user_attribute (any, optional) – Additional (meta) attributes defined by users. Same functionality to attribute, but with more understandable name.
user_function (func, optional) –
User-defined custom function that is automatically called when the timestep is incremented (more precisely, when update() is called). It takes only one argument: the Link object itself. Example: The following code prints the current number of vehicles on the link at each timestep. If user_function=None (default), no functions will be executed.
```
>>> def user_function(link):
>>>     print(len(link.vehicles))
>>> W = World(...)
>>> W.addLink("link", "node1", "node2, 1000, user_function=user_function)
>>> ... #define your scenario
>>> W.exec_simulation()
```
auto_rename (bool, optional) – Whether to automatically rename the link if the name is already used. Default is False (raise an exception).

speed¶

Average speed of traffic on the link.

Type:: float

density¶

Density of traffic on the link.

Type:: float

flow¶

Flow of traffic on the link.

Type:: float

num_vehicles¶

Number of vehicles on the link.

Type:: float

num_vehicles_queue¶

Number of slow vehicles (due to congestion) on the link.

Type:: float

free_flow_speed¶

Free flow speed of the link.

Type:: float

jam_density¶

Jam density of the link.

Type:: float

capacity_out¶

Capacity for outflow from the link.

Type:: float

capacity_in¶

Capacity for inflow to the link.

Type:: float

merge_priority¶

The priority of the link when merging at the downstream node.

Type:: float

Methods

`__init__`(W, name, start_node, end_node, length)	Create a link.
`actual_travel_time`(t)	Get actual travel time of vehicle who enters this link on time t.
`arrival_count`(t)	Get cumulative vehicle count of arrival to this link on time t.
`average_density`(t)	Get average density of this link on time t.
`average_flow`(t)	Get average flow of this link on time t.
`average_speed`(t)	Get average speed (=inverse of instantaneous travel time) of this link on time t.
`change_free_flow_speed`(new_value)
`change_jam_density`(new_value)
`departure_count`(t)	Get cumulative vehicle count of departure from this link on time t.
`in_out_flow_constraint`()	Link capacity updates.
`init_after_tmax_fix`()	Initalization before simulation execution.
`instant_travel_time`(t)	Get instantaneous travel time of this link on time t.
`num_vehicles_t`(t)	Get number of vehicles on this link on time t.
`set_traveltime_instant`()	Compute instantaneous travel time.
`update`()	Make necessary updates when the timestep is incremented.

Attributes

`density`
`flow`
`num_vehicles`
`num_vehicles_queue`
`speed`

actual_travel_time(t: float) → float[source]¶

Get actual travel time of vehicle who enters this link on time t. Note that small error may occur due to fractional processing.

Parameters:: t (float) – Time in seconds.
Returns:: The actual travel time.
Return type:: float

arrival_count(t: float) → float[source]¶

Get cumulative vehicle count of arrival to this link on time t.

Parameters:: t (float) – Time in seconds.
Returns:: The cumulative arrival vehicle count.
Return type:: float

average_density(t: float) → float[source]¶

Get average density of this link on time t.

Parameters:: t (float) – Time in seconds.
Returns:: The average density.
Return type:: float

average_flow(t: float) → float[source]¶

Get average flow of this link on time t.

Parameters:: t (float) – Time in seconds.
Returns:: The average flow.
Return type:: float

average_speed(t: float) → float[source]¶

Get average speed (=inverse of instantaneous travel time) of this link on time t.

Parameters:: t (float) – Time in seconds.
Returns:: The instantaneous travel time.
Return type:: float

departure_count(t: float) → float[source]¶

Get cumulative vehicle count of departure from this link on time t.

Parameters:: t (float) – Time in seconds.
Returns:: The cumulative departure vehicle count.
Return type:: float

in_out_flow_constraint()[source]¶: Link capacity updates.

init_after_tmax_fix()[source]¶: Initalization before simulation execution.

instant_travel_time(t: float) → float[source]¶

Get instantaneous travel time of this link on time t.

Parameters:: t (float) – Time in seconds.
Returns:: The instantaneous travel time.
Return type:: float

num_vehicles_t(t: float) → float[source]¶

Get number of vehicles on this link on time t.

Parameters:: t (float) – Time in seconds.
Returns:: The number of vehicles.
Return type:: float

set_traveltime_instant()[source]¶: Compute instantaneous travel time.

update()[source]¶: Make necessary updates when the timestep is incremented.