Additional bus priority facilities
The facilities in MOVA versions M4 to M7 for providing buses priority provide a fair degree of user-set flexibility in the way it reacts. However, when MOVA does react, the optimisation normally carried out is ignored. The facilities are used extensively in linked MOVA systems and the way it reacts is useful for such situations.
However, when providing buses priority, doing so at significant expense to other traffic is not always desirable, especially in busy periods, and any problems caused can mean subsequent buses suffer. Improving the way MOVA works in this area will have a significant impact. The additional facilities are as follows:
Including buses in stop and delay optimisation
To address the issue and yet still give buses a measure of priority, the MOVA stop and delay optimisation has been extended such that buses can be included with user-selectable weighting. For buses approaching on green, the weighting helps extend the green for them, giving them a better chance of continuing without being stopped. For buses stopped at red, the disbenefit for continuing the current green increases, which will tend to give the bus an earlier green. Hence MOVA will tend to favour buses to an extent that the user has some control over, but without ruining the operation of the junction to the detriment of other road users (and subsequent buses). The facility might also be useful for HGVs where it could be desirable to avoid stopping them – all that is required is the addition of selective detection.
Revised stage maximums for buses
The stop and delay optimisation algorithm in MOVA is used only when the junction is deemed to be undersaturated. During oversaturation, MOVA switches to an alternative algorithm that maximises capacity. In such conditions it is more difficult to provide buses with priority without causing too much disruption. Nevertheless, in order to provide some preference to buses, in MOVA M8, revised stage maximum times can be introduced when a bus has been detected. The maximums can be set to come into effect during just oversaturated conditions, just undersaturated conditions or both. Before reaching the alternative bus maximum times, MOVA operates as normal. This means that is possible to set a junction up such that it takes advantage of the ability to include buses in the stop and delay optimisation in undersaturated conditions and then in oversaturated conditions stages can be cut short on the way to the stage servicing the bus. All of the values are, of course, configurable.
Link-based PFACIL codes
Prior to MOVA M8 the bus priority facility used ‘priority facility’ (PFACIL) codes for each stage to determine whether and how a bus would get priority. A number of settings are available for each stage, but these could only be set once for each stage. This could be limiting, particularly if the facility was actually being used for linking MOVA junctions together. In MOVA M8 the PFACIL codes, which are still codes for a stage, can be set differently for each link. This provides the flexibility to take alternative action depending on which link the priority demand was placed upon.