formation, but also to take into account which infor-
mation is missing. For example, in Fig. 3 (C) the
ego vehicle (blue) is approaching the intersection and
an obstacle (a parked car in white) impede to detect
a pedestrian. For this given scenario, the first pedes-
trian (behind the obstacle) is not detected due to the
occlusion, but a proper scenario interpretation should
be able to interpret the occlusion as a critical miss-
ing information. Consequently, it is unclear if more
pedestrians approach the crosswalk or not.
1.2 Scenario Interpretation at Urban
Intersections
Due to the complexity of scenarios at urban intersec-
tions, it becomes obvious that a proper scenario in-
terpretation is required. In recent years several meth-
ods have been proposed to tackle this problem. Vacek
et al. (Vacek et al., 2007) present an approach for
a case- and rule-based situation interpretation using
description logic. The raw data from the sensors is
stored and transformed into a higher level represen-
tation. The different expected behavior of other ve-
hicles generates the linkage of other cases over time
with corresponding probabilities for every different
situation. Since the number of different options be-
comes very large at intersections, the computational
cost for the description logic reasoning constitutes the
main drawback of this approach. Logic description is
also used by Huelsen et al. (H
¨
ulsen et al., 2011) to de-
scribe an ontology that represents the road networks,
objects, their relations and the corresponding traffic
rules. The goal is to reason relations, objects, traf-
fic rules (e.g. hasRightOfWay or hasToYield) using
inference services. Even keeping only necessary in-
formation for reasoning, the main drawback of this
approach are the high computational costs. There-
fore, this approach is insufficient for real-time com-
putation.
Geyer et al. (Geyer et al., 2011) present a method
based on the cooperation between the driver and the
system with the Conduct-By-Wire (CBW) concept.
Depending on the current driving situation, and the
required information, the so-called gates are identi-
fied. A driving situation is described with three types
of parameters: Static (road network, traffic rules, pri-
ority, etc), dynamic (objects, traffic lights phases, etc.)
and diverse (weather, road conditions, etc.). The sys-
tem analyzes the required information at the gates.
Consequently, different automation levels are set to
make easier the cooperation between the system and
the driver. To determine which information is needed,
a occupancy map and entry directions at the intersec-
tion are set. The CBW approach was also used by
Schreiber and Negele (Schreiber et al., 2010) to de-
velop of a maneuver catalog from the driver point
of view. The focus is to analyze what the driver is
expected to do. This information is combined with
a set of maneuvers that should cover every possible
traffic and driving maneuver. The authors in (Alonso
et al., 2011)present two methods for priority conflict
resolution (priority charts and priority levels) using a
vehicle-to-vehicle (V2V) communication system as a
requirement. The first method uses vectors to describe
the turning possibilities of all vehicles and their corre-
sponding priority signs. Then, an auxiliary table con-
taining all possible vectors associated with Boolean
values is used to indicate if the ego vehicle has to
move or stop. This table contains 111 different cases
without considering the traffic signs combinations (3
for one vehicle, 27 for two vehicles, and 81 for three
vehicles). On the other hand, the second proposed
method aims to determine whether the ego vehicle can
continue or must wait by interpreting the different pri-
ority levels (using an auxiliary truth table to detect po-
tential conflicts with other vehicles). The authors pro-
pose a flowchart to handle the right of way problem.
These two proposed methods depend on an specific
topology (in this case a two road intersection). More-
over, V2V communication is required. Although the
focus of (Lotz and Winner, 2014) is not to turn auto-
matically at urban intersections, the authors propose
a maneuver-based planning for automated vehicles.
Based on the desired maneuver (or set of maneuvers
over the time) the proposed system plans the proper
lane change by approaching the intersection. The ap-
proach was tested in a multi-lane road network with-
out other road users.
2 PROBLEM DESCRIPTION
The described problem is focused on understanding
the perceived information of the environment at urban
intersections. In this sense, the interpretation should
enable to plan the proper vehicle motion for turn-
ing at urban intersections with different precedence
states. Unfortunately, there is no international regula-
tion that controls the traffic flow at intersections in a
unique manner for all the possible scenarios all over
the world. Therefore, this work considers the regu-
lation described in the Vienna Convention on Road
Signs and Signals (for Europe, 2006) and the German
regulation (f
¨
ur Straßen und Verkehrswesen (FGSV),
2010) in particular. A coherent way to address the
problem is to describe an intersection in a simple
manner. Therefore, we try to make a conceptual de-
scription of the scenario answering three questions
Scenario Interpretation based on Primary Situations for Automatic Turning at Urban Intersections
17