Information Technology Reference
In-Depth Information
the lane to the left. If the gaps allow a safe change the vehicle moves to the left
lane. For the right free lane changes the simulator executes the following steps
parallel for all cars
n
:
Return to a Lane on the Right:
•
Step 0: Initialization:
For car
n
find next car in front
s
on the lane right to car
n
and next car
r
behind car
s
. Set
l
n
:= straight.
•
Step 1: Check lane change:
if
d
e
n,s
(
t
)
>v
n
(
t
) and
d
eff
r,n
(
t
)
>v
r
(
t
)
,
then set
l
n
:= right.
•
Step 2: Do lane change:
if
l
n
= right, then change lane for car
n
to the right.
Thus, a vehicle always returns to the right lane if there is no disadvantage in
regard to its velocity and it does not hinder any other car by doing so.
It should be noted that it is not possible to first check for all lane changes to
the left and to the right and then perform them all parallel without doing collision
detection and resolution. This comes because there are autobahns with three
lanes and more. To overcome this di
culty the simulator checks and performs
the left lane changes in every odd time-step and the right lane changes in every
even time-step. For a systematic approach to multi-lane tra
c, i.e., lane-changing
rules, see, for example, [17]. For a detailed discussion of the different models see
[18,19,20] and the references therein.
3 Network Structure
A crucial point in the design of every simulator is the representation of the
road network. Like in other simulators (e.g., [1,21]) the network consists of basic
elements, links and nodes. A link is a directed bundle of parallel lanes or, more
casually, simply a piece of autobahn. A vehicle on a link has local coordinates
(cell and lane) with respect to the link. A node is a connection between two
links. It stores information about where the exit is on the link to be left, about
how to leave the link (lane change, drive out of it), and how to calculate the new
local coordinates on the target link (cell offset, lane offset).
By combining links and nodes one is able to build the complex structures of
the autobahn network. Examples for these structures are:
•
junctions, where vehicles enter or leave the autobahn,
•
intersections, at which two autobahns are connected, and
•
triangular intersections, where two autobahns meet, but one ends.
The complexity of an intersection can be derived from Fig. 2. Other geome-
tries are rarely found in the autobahn network in NRW. However, they can be
constructed easily with the elements used here.
