3 Terms and definitions

Bridges are modeled as objects in ASAM OpenDRIVE. The road with the bridge object leads over a bridge. Bridges are valid for a road’s complete cross section unless a lane validity record with further restrictions is provided as child element.

Common junctions are the default type of junction in ASAM OpenDRIVE and specify areas where drivable lanes may overlap and traffic may cross.

Connecting roads are part of a junction and link the roads going in and out.

Crossings are junctions without connecting roads. They define sections where crossing traffic can appear. Traffic does not change roads at crossings, for example, at railway crossings.

Direct junctions are intended to model entries and exits where drivable lanes may overlap to split or merge, but traffic does not cross.

Entries are locations where roads merge into another road. Entries are not the same as the entry value of the @type attribute at the <lane> element which is used for the acceleration lane.

Exits are locations where a road splits into other roads. Exits are not the same as the exit value of the @type attribute at the <lane> element which is used for the deceleration lane.

Incoming roads contain lanes that lead into a junction.

An inertial coordinate system is a right-handed coordinate system according to ISO 8855.

Junctions model intersections between roads.

Junction groups indicate for routing that the grouped junctions belong to the same node and are commonly seen as one big junction, for example roundabouts or highway interchanges.

Lanes are an essential part of all roads. Lanes are attached to the road reference line and are defined from inside to outside.

Lane offsets shift the center lane away from the road reference line.

A lane section splits a road into multiple parts whenever the number of lanes or their function changes.

A lane has one lane type that defines its function, for example, driving, biking, or exit.

Lane validities restrict signals and objects to specific lanes.

Lane widths widen or narrow lanes along the t-coordinate within lane sections.

A local coordinate system is a right-handed coordinate system according to ISO 8855.

Objects influence a road by expanding, delimiting, or supplementing its course. Objects are elements that form the environment, for example, buildings, guard rails, poles, and trees. Objects do not influence the behavior of traffic directly, unlike signals.

Outgoing roads are not specifically defined as an element or attribute in ASAM OpenDRIVE. Incoming roads serve as outgoing roads. These roads are implicitly defined as outgoing by the connecting roads that lead into them.

Roads are the core elements for any road network in ASAM OpenDRIVE. Each road runs along one road reference line.

Road elevation specifies the elevation along the road reference line, that is in s direction.

Road markings in ASAM OpenDRIVE are defined as lane markings, object markings, for example parking boxes, or signals, for example stop lines.

A road reference line defines the horizontal alignment of a road and consists of one or more geometry elements. Every road has one road reference line. Further properties of the road, for example, lanes, signals, and objects are defined relative to the road reference line.

The road reference line is always located within the x/y-plane defined by the inertial coordinate system. A road reference line coordinate system runs along the road reference line. It is a right-handed coordinate system. The s-axis follows the tangent of the road reference line. The t-axis is orthogonal to the s-axis. The right-handed coordinate system is completed by defining the up-direction h orthogonal to x-axis and y-axis.

The s-coordinate is defined along the road reference line, measured in meters from the beginning of the road reference line.

Signals are traffic signs, traffic lights, and specific road markings for the control and regulation of road traffic.

A signal controller applies a signal cycle (see signal cycle) to a signal or a signal group (see signal group).

A signal cycle is an ordered list of phases (see signal phase) for one dynamic signal.

Signal dependencies limit or extend the validity of one signal by an additional signal. For example, a speed limit sign of 60 km/h that is only valid for trucks, specified by a supplementary sign. One signal may have multiple dependencies.

Each dynamic signal needs to be in exactly one signal group.

A phase of a dynamic signal is the semantic state (see signal state) in combination with a (possibly infinite) duration, which specifies how long this semantic state is active. This term is not to be confused with the English civil engineering term stage or the German term phase.

Signal references link a signal to another signal or object. One signal may have multiple signal references. The signal reference term should not to be confused with the <signalReference> element that is used to link a signal to multiple roads.

A state of a dynamic signal is the combination of the semantic and the observable state of a signal.

Multiple signal groups (see signal group) which should be kept synchronized and whose signal cycles (see signal cycle) have the same finite duration can, but are not required to be mapped to a synchronization group. This mapping can be used to indicate that whenever the phase of one signal group is set, by an ASAM OpenSCENARIO TrafficSignalControllerAction or otherwise, the other signal groups in that synchronization group should be set to the corresponding position in their signal cycles.

On a slip lane a driver can change roads without driving into the main intersection.

Collection of connected roads enriched by static objects that do not change during runtime of a simulation.

Superelevation specifies the transverse slope along the road reference line. Superelevation is defined for a cross section and can vary in road reference line direction.

The t-coordinate is defined as the lateral position orthogonal to the road reference line.

Tunnels are modeled as objects in ASAM OpenDRIVE. The road with the tunnel object defines the part of the road that is the tunnel or the underpass.

Virtual junctions manage connections within an uninterrupted road, for example, entries and exits to parking lots, and pedestrian crossings.

Variable message boards can change their values during the simulation in ASAM OpenSCENARIO.