Learn about Signposting in Paramics network

UPDATED: August 22, 2017

Signposting is not a literal term, it is a subjective term used to define the point at which individual vehicles become aware of upcoming hazards in the network. Hazards are defined as points inherent in the network that require a vehicle to be in a specific lane to perform a maneuver. Hazard examples would include priority intersections, roundabouts, signalized intersections, lane drops, off ramps, on ramps, freeway diverges, freeway confluences etc.

When a vehicle recognizes a hazard, via the signposting, the vehicle's lane range will be reset appropriately, which will then have one of two effects:
  • The lane the vehicle is in is within its lane range and the vehicle does not need to make any lane changing maneuvers.
  • The lane the vehicle is in is outside its lane range and the vehicle is required to make an appropriate lane change (or series of changes) in order to be within the specified lane range for the hazard.
A vehicle can only be affected by one hazard at a time, the next downstream hazard, if it has been recognized. Vehicles outwith the limits of a signpost will have their lane range set by the simulation engine, which is based on the vehicle attributes.
User-added image

Screenshot shows the signposting to a signalized intersection with a left turn (right hand drive network). This indicates that the hazard is on an urban link and the Signal Left Turn  is the type of hazard.

As detailed above the pink line is where the most aware drivers (awareness 8) will see the hazard and the blue line will be where the least aware drivers will see the hazard (awareness 0) with a spread of points between these two limits. Golden rule says that Hazards vehicles can only see one hazard at a time however Lane choice rules allow an override to this premise.

Signpost distances/range is a subjective parameter and based on observation and engineering judgment. It is highly probable that during the course of the day (dependent on traffic volumes) that signposting distances will vary. Signposting distances will tend to be longer when traffic volumes are higher and there are fewer gaps available for vehicles to change lane.

Signposting can play a major part in network calibration as in high flow freeway situations shockwaves caused by late lane changing, forced lane changing, stuck vehicles and lack of signpost range can all lead to shockwave behavior that is not representative of the network.


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