2DXT                                                                                          New highway intersections in one level
Intersections are partially simplified

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

 

 2DXT                                                                                      New highway intersections in one level
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