Reference for setting Traffic Simulation Parameters for Terms, Behaviors, Restrictions and Vehicles.
Terms
- A start time, normally specified as HH:MM.
- An end time, also normally specified as HH:MM.
- A day of the week, by default “AnyDay”, but can be something more specific.
You can have as many Terms defined for your model as you require. They can overlap, or be sequential. A lane restriction can be defined to have one term (for example “buses only” defined for 07:30 to 09:30) while a demand profile is defined to have another (for example “AM Peak” defined for 07:00 to 10:00).
- Always – Where a term is required, selecting this term ensures that the parameter to which the term is attached applies all the time, even if the simulation term is changed. This term cannot be modified.
- Simulation – This is editable, although the name cannot be changed. This term defines the start and the end of the simulation period.
Parameters - Behaviors
A behavior defines a number of parameters controlling decisions made by each person in the model.
Behaviors are assigned to person-types or vehicle-types; each person or vehicle generated has one of these types. When a person makes a multi-stage trip, and becomes the driver of a vehicle, that vehicle inherits the behavior from the person. Separating Behavior from the type of person or vehicle allows you to separate the physical constraints from behavioral constraints, and to define a range of types that incorporate combinations of ranges of each.
For example, you could define an aggressive behavior and a passive behavior, and then go on to associate each of those behaviors with a range of physical vehicle types, such as car, van and truck.
Another advantage of separating behavior from physical constraints is that the Behavior can be retained when modelling a multi-stage journey. For example, if a journey is made up of a car trip, followed by a pedestrian trip (walking from the car park to the station), followed by a public transport trip, all three trips can be modeled using an agent with a consistent behavior.
Parameters / Behaviors / Mobs
A Mob (mix of Behaviors) is a group containing any number of Behaviors. A Behavior can be in any number of Mobs.
When a new Behavior is created, a new Mob will be created automatically, with the same name, containing initially that one Behavior only.
Restrictions affecting how vehicles can use lanes are defined in terms of Mobs.
Parameters / Behaviors / Mode Choices
The Mode Choices tab contains the "master switches" that control which modes of travel are available to each Behavior in the model. For example, if you want to define a Behavior that will always drive, rather than take public transport, setting a Mode Choice accordingly for that Behavior is how to do it. Similarly, you can define behaviors for people who prefer to cycle, taxi, or have a driver drop them off at their destination or pick them up at it later.
The Mode Choice switches available are:
| Can Walk | True if a person of this Behavior can use walking as a mode of travel in the model. |
| Can Drive | True if a person of this Behavior can drive to a parking zone or a transition zone in the model. |
| Can Ride | True if a person of this Behavior can take public transport. |
| Can Taxi | True if a person of this Behavior can take a taxi, if a taxi is available.
Even if this is true, the cost of taking a taxi will still be taken into account in calculation of the lowest cost route to the destination. Setting Can Taxi = False rules out taking a taxi. The sections below explain how the Traffic Analyst assesses costs for each mode of travel. |
| Can Cycle | True if a person of this Behavior will cycle, and a cycle vehicle type exists. |
| Can Be Dropped Off | True if a person of this Behavior can be dropped off at a designated drop-off zone. This mode implies that this person has a car and driver available and thus will not need to spend money on parking. For example, when dropping someone off curb-side at an airport. This may often be the least expensive option when traveling to a destination that also offers pay-parking . But in many cases a small fraction only of the population will have a car and driver available for a given trip. |
| Will Be Picked Up | True if the person of this Behavior will be picked up a designated pick-up zone. If this mode switch is set to True, then no other mode is considered except for the cost of walking from the origin point to the pick-up point, if Can Walk is also True. |
Behaviors / Walking Costs
Can Walk: True if a person of this behavior can use walking as a mode of travel in your model.
| Walk Cost/second | The value of time for walking, specified in small currency units (pence, cents, etc.) per second. |
| Walk Cost/distance | The value of distance for walking, specified in small currency units (pence, cents, etc.) per long distance unit (km, mile). |
| Walk Cost/base | A basevalue walking cost, used to bias the cost of short versus long trips. |
Behaviors / Driving Costs
| Drive Cost/second | The value of time for travelling in a private vehicle (car, van, truck, etc.), specified in small currency units per second. |
| Drive Cost/distance | The value of distance for travelling in a private vehicle (car, van, truck, etc.), specified in small currency units per long distance unit (km, mile). |
| Drive Cost Base | A private vehicle base cost, used, for example, to model the base cost of ownership of a private vehicle. |
Behaviors / Transport (Ride, Wait) Costs
| Ride Cost/second | The value of time for traveling on public transport, specified in small currency units (pence, cents, etc.) per second. |
| Ride Cost/distance | The value of distance for travelling on public transport, specified in small currency units per long distance unit (km, mile). |
| Ride Cost/base | A base public transport cost, used, for example, to model the base fare payable. |
| Wait Cost/sec | The value of waiting for public transport, specified in small currency units (pence, cents, etc.) per second. |
Behaviors / Parking
| Park Duration |
A time, in hours, used to calculate the cost of parking. The premise for this parameter is that a person with this behavior is planning an outward-return journey, and intends to park for the specified duration. For example, a person working in a city centre may park for 8.5 hours during a working day. A business traveller going to an airport may be staying at their (air) destination overnight, and be planning a stay of 36 hours at the airport, from 07:00 Monday to 19:00 Tuesday |
| Parking Vehicles |
A (demand) division of vehicle types to use when selecting from parked vehicles. A demand division has % values to generate vehicles in proportion when
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| Optimist | If this parameter is ON, the driver will always assume that there is still a free bay in the most popular area. If it is off, the driver will take the first available space. |
Behaviors / Driving
| (Speed) Compliance | A multiplier, by default 1.0. This is used for vehicles to specify the "perceived" speed limit on any road. Multiply the signed speed limit by this parameter to obtain the perceived speed limit that will be used as the maximum speed a vehicle will attain if unconstrained by other vehicles or lane geometry. |
| Minimum Gap | A distance, in metres, used to specify the minimum spacing between stationary vehicles in congestion. |
| (Target) Headway | A time, in seconds. This is used in the vehicle-following algorithms. |
| Reaction Time | A time, in seconds, used in the vehicle-following algorithms. |
| Safety Margin | Used to calculate stopping distance. The absolute minimum stopping distance is derived from current speed and (constant) maximum deceleration is multiplied by this safety margin. |
| Lane (Change) Gap | A time, in seconds, used for the lane changing algorithm. A larger value means that a larger gap will be required, making lane changing more conservative. A smaller value for lane changing gap will make lane changing more aggressive. |
| Variability | A number between 0.0 and 1.0. The variability of: (speed) compliance, reaction time, target headway and minimum gap distance defined in terms of standard deviations relative to the mean. So a value of 0.1 would mean that a distribution would have -1SD to +1 SD from 0.9x mean to 1.1x mean. Set this to a non-zero value to make the behavior of your agents less uniform. |
Behaviors / Routing
| Drive Spreading |
For road routes, the relative increase in cost of an alternative route over the least cost route that an agent may consider acceptable in choosing a route. Referred to also as the "perturbation" value. |
| Walk Spreading |
As for Drive Spreading (above) but for walkway routes. |
| Cost/price |
The perceived value of money for any agent with this behavior. This is applied to any tolls or other charges along the length of the route before these are included in the generalized cost equation. |
| Dynamic Routing |
If on, then any agent with this behavior will receive cost feedback updates, if cost feedback is enabled in the appropriate routing window (Assignment → Vehicle Routes or Assignment → Person Routes). You might use this to model two sets of vehicles; one whose drivers receive updates during their trips (perhaps by radio) about the state of the traffic, and another whose drivers have a static view of the cost information on the network. |
Restrictions
A vehicle restriction is applied to a lane, to control the types of vehicles that move on that lane. Vehicles are filtered for a restriction by behaviour. A Speed Control is similar to a restriction, applying a speed limit to selected vehicles.
To create a restriction for a group of behaviours, you must first create a Mob to give a name to the selected group of behaviours. If you want to apply a restriction to a single behaviour, it is likely that a Mob containing only that behaviour already exists, as one is automatically created, with the same name, when a behaviour is created.
A Restriction has the following fields:
| Name | Numeric name for the restriction which is created automatically and is unique. |
| Description | Descriptive name for the restriction, of any length, which need not be unique, but for clarity, a unique description is better. |
| Color | Color for the restriction, used when the appropriate Feature is enabled in the Layer Pane. |
| Term | Time period defining when the restriction applies. |
| Mob | A single behaviour or group of behaviours to which the Restriction applies. |
| Permission | Barred, or Allowed, or Mandatory
You can create a restriction to bar all behaviours in the mob or to allow all behaviours in the mob. Mandatory applies to lanes only. It forces all behaviours in a mob to use that walkway or lane, even if alternatives exist. Thus you can create a bus lane and make it mandatory for bus drivers. |
| Distance from the end of any lane beyond which any vehicle may use the lane. For example, if the left hand lane is a bus lane, but pocket is defined as 50 metres, left-turning cars may use that lane for the last 50 metres before the stop line. |
Vehicles
Each vehicle in the model has a Vehicle Type. The Type specifies parameters which control the size, movement and display of the vehicle in the model.
- Small Car
- Medium Car
- Large Car
- Small Truck
- Large Truck
You edit parameters for Vehicle-Type in several tabs, as described below.
Vehicle Description Tab
| Name | A unique number, created automatically, not editable. |
| Description | A textual description for the type, of any length, which need not be unique, but for clarity, a unique description is better. An example might be “Generalised Car” or “Small Truck”. |
| Behavior | The Behaviour(s) associated with this vehicle type. |
| Color | A colour for identifying vehicles of this type. If the colour is black, then the vehicle is coloured according to the layer. It is also possible to colour a vehicle by its driver type, using an option on the Tags window, accessed from the Display menu. |
| Solid Shape | Used to set the 3D shape used in Solid display mode. If it is not set, a solid shape will be assigned based on the size of the vehicle and the name of any shape group. |
| Solid Group | Used to associate a vehicle type with a set of 3D shapes, so that all instances of a type do not look the same in the detailed display mode. When a vehicle of this type is created, it will select one of the shapes from the group at random. |
| Taxi | A taxi type can queue in a taxi rank, pick up a passenger at the head of the rank, and drop off a passenger at a drop-off zone. |
| Cycle | Cycle vehicles are counted separately to other vehicles. |
| Emergency | Emergency vehicles have different rules for lane use, and can exceed the posted speed limit. |
Vehicle Size Tab
| Length, Width, Height | The mean dimensions of the vehicle, in metres or feet. To generate a distribution of sizes, see Size Variation. |
| Mass | The mass (“weight”) of the vehicle (kg or lb). |
| Size Variation | A value specified as a fraction of each dimension, used to specify the standard deviation of a normal distribution for each dimension.
For example, if the mean length of a vehicle type is 4.0m and the size variability is 0.1 or 10%, the lengths of vehicles of this type will follow an approximate normal distribution of mean 4.0 metre and standard deviation (SD) 0.4 metre. (The distribution is clamped to 3xSD around the mean to avoid unexpected values such as negative or zero lengths.) |
| Side Gap | The minimum gap to the side of a vehicle when passing another vehicle in the same lane. |
| Extras | The number of extra people to count for this vehicle. It is not necessary to include a value here for the driver of a taxi or a drop-off or pick-up vehicle; these are counted automatically. This field should be used for additional people that you want to count in the Extras section of the trip summary statistics. |
| Load Base | The vertical distance up from the road surface defining the base of the load for freight or people carried by this vehicle. |
| Load Front, Back | The horizontal distances from the leading edge of the vehicle to the load, and from the trailing edge of the vehicle to the load. |
| Load Side | The horizontal distance in from the sides of the vehicle to the load area. Set this to any non-zero value to display people. |
| Load Capacity | The maximum mass of the load (kg or lb). |
Vehicle Dynamics Tab
| Tire Friction | This value controls the maximum speed at which a vehicle can turn a corner. The default value for this parameter is 0.8. |
| Gap Factor | This multiplicative factor is used to increase or decrease the gap to other vehicles behind vehicles of this type. You might use this to increase the distance of queuing vehicles behind large trucks. In effect, this parameter makes vehicles of this type appear longer than they are to other drivers. |
| Conflict Factor | This multiplicative factor is used to increase or decrease the cross and merge times where streams intersect, on a per-type basis. You can use it to adjust the gap acceptance at intersections on a type-by-type basis. See also the Cross and Merge time parameters for a Stream. |
| Keep | The preferred side of the lane. Normally, this is set to None, which indicates that a vehicle will aim to drive along the centre of the lane in the absence of other traffic. However, for some vehicle types, such as cycles, you may want to set this to Left or Right. |
Vehicle Attachment Tab
| Controls | The leading agent has this field set, describing the vehicle type that it is pulling or controlling. |
| Attachment Angle | The angle of attachment, clockwise in degrees, of the attached type, relative to the direction of motion. For a trailing vehicle, this would be 180. |
| Attachment Distance | The distance from the periphery of the leading type at which the attached type will pivot. An articulated truck might behave best if this is set to a negative number, which makes the trailer overlap the cab. The total length of this cab-trailer combination is the sum of the lengths of the two types, plus the attachment distance. So for example, if the cab is 5 metres long and the trailer is 12 metres long, and the attachment distance is -1m, the total length will be 5 + 12 – 1 = 16 metres. |
| Attachment Count | This value is set to 1 by default if there is an attachment, but it can be set higher if you want to repeat the attachment.
For example, if you want to create a road train with one truck and 2 trailers, first define a Trailer type, then define a Truck type with fields:
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