Innenliegende Linkseinfädelungsstreifen an plangleichen ...

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Inner left merging lanes at single-level
junctions in towns and in advance areas of
built up areas
The aim of the investigation was the examination of
road junctions with inner left merging lanes (iLES) in
terms of performance capacity and traffic safety as
well as the representation of application limits and
design notes.
Within the framework of the research project,
empirical studies were conducted at 10 junctions with
iLES. The average daily traffic concentration at the
junction, the peak hour, time gaps in the peak hour as
well as waiting times and tailback lengths at the
junction were determined. In addition, the
acceptance of an established iLES and the areas
where one changes from the iLES to the continuous
traffic lane were recorded.
Within the framework of a macroscopic accident
analysis at 50 junctions, a total of 816 accidents were
analysed for the years 2006 until 2008. For all
junctions, the relevant accident parameters were
determined (accident costs, accident density,
accident rate, accident cost density, accident cost
rate), and the types of accidents (one digit and three
digit) were analysed. As a whole, it could not be
determined that junctions with iLES are less safe
than junctions without iLES, or if they are remarkable
in any other respect.
The analysis of the accident diagrams in the context
of the microscopic accident analysis at 10 junctions
showed two significant accident occurrences which
can be associated with the iLES: Collisions by drivers
turning left inwards with drivers turning left outwards,
at the point of changing lanes from iLES to the
continuous traffic lane. There were hardly problems
involving cyclists or pedestrians, which can be
partially attributed to the fact that the pedestrian and
cyclist traffic only plays a subordinate role in the
investigated examples.
A delimitation of the application area of road junctions
with iLES compared to road junctions without iLES or
with LSA was performed by determining the waiting
times in the subordinate access roads for all three
junction types at various junction traffic levels and
load situations. From this, on the one hand the limit
was determined, from which a junction without iLES
is no longer efficient and an iLES would be a sensible
implementation, and on the other hand the limit was
determined from which signalling would be
advantageous compared to iLES.
The HBS method was modified for the method of
determining the waiting times at the junctions with
iLES. For this, "Strom" (flow) 8 was neglected and
other values determined within the framework of
the research study were used for the limit and time
gaps.
In order to incorporate the experience made by the
legally responsible authorities within and before the
building up of areas, an expert workshop was held in
Frankfurt am Main on 6 October 2010. The
discussion contributions resulted in a number of
references which could be incorporated in the
described results.
A road junction with inner merger lanes (iLES) can be
employed as an alternative to a non-signalled
junction if otherwise insufficient traffic quality would
be achieved or if the traffic quality is to be improved.
An iLES worsens the ability to cross the super
ordinate junction arms for pedestrians and cyclists
considerably. The use of iLES is thus in contradiction
with the needs of pedestrians and cyclists. They
should only be employed if no particular
requirements for crossing exist.
Within built-up areas the length of an iLES should be
between 30 and 60 m, before built-up areas with
speeds of over 50 km/h, this should be 60 to 100 m.
Too great lengths should be avoided in order to
prevent the impression of an overtaking lane.
In the marking of the lanes, particular attention
should be paid to the understanding of the traffic
control being supported. Additionally, signs should be
used which explain the traffic control. These should
be deployed both in the subordinate access lane and
the super ordinate access lane located to the right.
The original report contains as an appendix, graphic
illustrations of the essential results of the surveys at
the ten examined junctions (e.g. tailback length and
accident diagrams) as well as a tabular overview of
the waiting times used for the calibration of the
simulation. The reproduction of these annexes was
omitted in the present publication. They are available
at the Federal Highway Research Institute and can
be viewed there. References to the annexes in the
body of the report were maintained for the reader's
information.