A metering is a device to regulate the flow of vehicles. Typically this is a car park barrier,a toll gate or a ramp meter on a freeway. A metering holds back the flow of vehicles and releases them according to the type of meter; these are:
- Green-time metering and Green-time by lane metering: The metering is a traffic signal with fixed or variable times.
- Flow metering: The metering aims to give a specified flow rate to pass it.
- Flow-ALINEA metering: The metering implements the Alinea algorithms for ramp meters.
- Delay metering:The metering delays each vehicle by specified time.
Note that while a meter can be positioned at any location in a section, in mesoscopic simulation, all meterings will be applied at the end of the section.
A meter can be created using the Metering Tool. Click on the tool in the tool bar then select the section and position where the metering is to be located in a 2D view.
Once the meter is located on a section it can be translated to any position along the section by selecting and dragging it using the mouse. The meter can also be adjusted to cover a subset of lanes on the section by dragging the selection handles on the meter edges or to cover a length of a section by dragging the meter edges. If the meter is to be moved to a different section, press the Ctrl key when selecting and dragging it using the mouse to the destination section. Double clicking on the metering will bring up the properties editor to set the appearance of the meter and its control actions.
The context menu for the metering contains options to label the metering with its ID, or with a Dynamic Label to show any of the attributes of the metering appropriate to its type of operation i.e. the Green Time per Lane if the metering has that property.
Ramp Meter Editor¶
The metering name and external ID are set here as well as the type and the visualization in 3D
The control type for metering is set in the Metering Editor, the detail of how a control is configured is described under the Metering Topic in the Control Section.
A metering can be drawn as a Traffic Light, as a Barrier or it can be invisible. The time taken for a barrier to move from the stopped (horizontal) position to the open (vertical) position is specified in the 3D Preferences section.
A mesoscopic simulation does not include acceleration and deceleration components in its car following model and hence, vehicles in a mesoscopic simulation are always considered to use their target speed. This simplification is mesoscopic simulation is important in all situations were the acceleration and deceleration plays an important role in the calculation of vehicles travel time. In particular the delay metering option, used in a mesoscopic simulation, only applies an extra delay time to all vehicles affected by the meter. Hence, vehicles going through a meter will not be simulated to stop at the meter point, wait the delay time and then accelerate to achieve their target speed. They are only penalized with an extra delay time. It is therefore not possible to compare, in detail, two simulations using mesoscopic and microscopic behavior models when the model includes a meter.