The New Type of One Level Intersection with
Continuous Traffic Flow on the Main of the Intersected Roads
Dr.-Ing. Alexander Cuzinov
The Main Two Elements of Pendulum Type Intersections and
Brief History of Their Elaboration.
At
the beginning of the last century the interchanges had widely been
elaborated and implemented. It had given the opportunity to
increase the total capacity of roads and to organize the
continuous traffic.
Already in the second half of the
century, because of the interchanges high costs and demands in
city territories, more cheap and compact interchanges decisions such as
Cloverleaf and its modifications were used more and more often. Along
with it, and it can be said, because of this reason, transport
engineers started their attempts of further improvement of one level
intersections. In 70-80-s one level intersection with continuous
traffic in all directions was elaborated. It was patented (Fig. 1) in France (a) in 1972 and in USA (b) in 1966.
Fig. 2
demonstrates the principal scheme of this intersection and consequence
of its transformation from simple crossroad. According to the main
functional principle this type of intersections can be named - the
pendulum intersection. Its main idea is the traffic flow
branching out the separate equal parts in two directions. These two
traffic parts intersect together synchronically already in some
simple crosses that entirely form one great intersection with continuos
traffic. After the passing through these simple crosses the both
traffic parts connect together just again. For transport engineers it
is surely evident that this intersection may forever remain only as a
theoretical one, although its effectiveness could inspire its founders
for the patenting. The practically implemantable modification of
this intersection was patented in 1975 in USA by Kaufmann (Fig. 3).
Fig. 1 a - Patent Nr. 2098493, France, 1972
b - Patent Nr. 3272097, USA, 1966
Fig. 2
Fig. 3 Patent Nr. 3915580, USA, 1975
Unfortunately
the very theory of the consequence of the cross transformation in this
type of intersections had not been noticed or had consciously been
omitted, because of the inspiration with the final result. There had
been missed a theoretical preliminary step – the intersection with
continuos traffic in one of the intersected direction. This theoretical
step is a base of the first main element of the suggested intersection
type which is described in this article.
The second element of this intersection is the element of one level
intersection, worked out in Great Britain and described by R.M. Kimber
and Marie C. Semmens. This element is stretching out of group of
vehicles along the stop-line (Fig. 4).
This element corresponds more to the probable features of traffic
flow than the vehicles accumulation in the convoy in front of the
stop-line. The implementation of this element reduces duration of
traffic light phases and allows to reduce the time losses and,
thus, to increase traffic capacity.
Fig. 4 Kimber and Semmens, 1982
Traffic Organization on the Pendulum Intersections
The pendulum intersection is expansion of the main of crossing roads (Fig. 5). This expansion includes 5 parts: the middle roadway; two side roadway as well as two accumulation zones, that are used for temporal stops by traffic direction changes. The size of these intersections depends on the accepted estimated speed of the continuos movement on the main road.
Fig. 5
This type of intersections has a huge amount of modifications. The main intersection is shown on the figure 6
(Variant 1). Variant 2 has the left turn from the headway
from the left line. Vehicles move in the following way: on the
middle roadway it goes continuously. Simultaneously the first
accumulation zones are being filled up from the side roadways with the
transport turning to the left from the headway (Phase A). This
"left-turns phase from the headway" lasts approximately 20 seconds.
After that there follows the filling of these accumulation zones with
the vehicles from the minor street. Simultaneously the vehicles,
situated on the second accumulation zones, leave it. This is the phase
B - "the phase of filling and departure of accumulation zones" that
continues also approximately 20 seconds. Before the start of the third,
the main phase there is a (so-called) subphase - the transformation of
continuous traffic flow from the middle roadway onto the side ones. The
traffic is being transformed with the time displacement (lane by lane).
This displacement takes approximately 5 seconds. The third phase -
phase C is the phase of vehicles replacement from the first zones onto
the second zones. Simultaneously the left turns from the minor street
are being realized there. After that with the time displacement lane by
lane traffic is being replaced back from the side roadways onto the
middle one. And here the new cycle starts. The cycle continues
approximately 70 seconds.
The same principle was used for working
out of 5 variations of such intersections in the streets with one
of one-way traffic.
Fig. 6 Variant 1
Fig. 6 Variant 2
Traffic Capacity of Pendulum Intersections and
Time Losses in these Intersections
The
proposed intersections have approximately 1,5 times higher total
capacity than traditional one-level intersections. The lost time on
these intersections for one participant of traffic do not overgo the
lost time on the usual crossing.
Fig. 7 gives the simplified comparison of capacities and Fig. 8 demonstrates one of the results of mathematically simulated intersection.
Fig. 7 Symplifyed comparison of the capacities
Fig. 8
Here it is very important to underline, (it could be seen from the
graphical diagrams), that traffic capacity rises along with increasing
of the volume of accumulation zones only up top the certain
level. The following increasing of the volume of
accumulation zones does not lead to the increasing of traffic capacity.
That is why, existing methods of calculation of traffic capacity of
one-level intersections can not be used for this type of intersections.
With the accumulating zones of aprox. 21 m. length already the maximum
capacity of the minor road ( 1000-1800 veh/h in two lines) is
reaching, what corresponds to 70-sec. traffic light circle.
The total capacity of intersection on the urban highway in one
direction reaches 3-4,5 thousands of veh/h and 1-1.8 thousands of veh/h
- on the minor road (incl. by turns to the left -up to 300-600 veh/h
and 600-800 veh/h - by turns to the right).
New type of intersections has been developed as a solution of the contradictions between demands of public transport for traffic network from one side and the demands of a private transport for traffic network from the other side. Having a high level of private transport development it is necessary to construct the continuos traffic headways network. For the effective operation of public transport it is worthy to have the high density of streets network. The continuos traffic headways network cuts a city into the large separate districts. In this case the convenient city transport communication is being broken. Moreover, an ineffective overrun of transport arises in the whole road network (Fig. 9).
Fig. 9 2,0 q 1,5 q 1,0 q
Nowadays
the interchange “Diamond” is used on the crossing of the road with
continuos traffic with the road with regulated traffic. The use
of proposed intersection in such cases ( instead of “Diamond”
interchange) could be more effective and be more widely applicated,
because of its costs, that are approximately in 15-20 times lower than
that of interchanges, and, moreover, the described intersections
occupy in 2-4 times less of city area (the area of these intersections
is 5000-20000 m2).
The proposed intersection mostly corresponds to the character of cities
roads loading (headway’s have a transport loading in 3-4 times higher
than minor streets).
The application of these intersections allows to raise the level of
coordinated traffic (“green wave”) in the roads network. (For traffic
flow in the headway it is not important in what time point it will
change the traffic lanes).
New type of intersection for highways
The
intersections of pendulum type are developed especially for the
highways – motorways that are different in their geometry, size and
occupied territory from the intersections of the same type on the city
roads.
Figure 10 shows the main type of
this intersection. It allows the continuous traffic with the maximal
speed of 80-100 km/h along the main direction. (The speed in the place
of intersection).The length of the intersection of pendulum
type is 400 m, the width – 250 m, the occupied squire – between 4,0-4,2
hectares. The width of accumulation zone is 24,0 m. According to
European standards this size could be reduced up to 19,0 m.
Fig. 10. SX1, 2006
The suggested intersection could have 2 or 3 lines for the continuous traffic in one direction:
intersections with two lines could be used on the highways with four or
six traffic lines, which have the traffic density about 30-45 thousands
of ehicles per day in one direction. In the case of four lines highway
the exit from the highway should have tree lines, that continuously
narrows into two lines;
intersections with tree lines of continuous traffic are supposed
for the highways with 6-8 traffic lines, which have the traffic density
about 45-55 thousands of vehicles per day in one direction.
Intersections of pendulum type could be used for all types of
incomplete motorway junctions at different levels, where the major and
minor highways intersect.
Capacity of suggested intersections
Capacity
of intersections of pendulum type for motorways is equal to the
capacity of incomplete junctions at different levels, which are used
nowadays in the case of intersection of highway with the minor motorway.
The capacity of main road with two traffic lines in straight direction
is 3,0-3,6 thousands vehicles per hour (in one direction). In the
case of three traffic lines in straight direction the capacity equals
4,5-4,8 vehicles per hour.
The capacity of the minor motorway with two traffic lines in straight direction is 1000 – 1800 vehicles per hour.
The capacity for right turns is equal to the capacity of complete junctions – 800 – 1200 vehicles per hour.
The capacity for left turns is equal to the capacity of incomplete junctions – 300 – 800 vehicles per hour.
The loss of time in the case of left turns at the described
intersections and in the case of complete and incomplete junctions are
identical – the duration of the car movement in the case of left
turn at the intersection of clover leave type is 40 sec. The
increasing of the number of traffic lines for the left turn up to two
allows to increase the capacity comparable with the capacity of the
complete junction –1200 vehicles per hour. Optimal duration of the
street light is between 70 and 90-100 sec.
T-form intersections
Figure 11
shows T-form intersection, which is used for the part of
motorways, where the minor roads are connected with the major
roads. This type of intersection has two main phases. Its
capacity for the main road both in the case of straight direction and
right turns is identical to the capacity of the main type of
intersections. The capacity in the case of left turns is 900 – 1000
veh/h. The intersections of T- type could be of different form, size
and have diverse number of traffic lines at the accumulating zones and
at left turns. The organization of traffic in the case of this type of
intersection is simple; it could be easily regulated by technical
traffic equipment and provides the high traffic security.
This
type of intersection is very important for the countries with both high
and low territorial density, for example, Russia, Ukraine, Poland etc.
T-form intersections are most simple intersections in comparison with others, that is why the experimental construction could be started with this very intersection.
Fig. 11. ST1, 2006