We present a new solution for the highway interchange, which represents the best compromise between the traffic capacity, the land area used and construction cost. The difference between the known and the new solution is in the implementation of the opposite directional ramps which are widely separated in the area of the interchange. In the middle, between the directional ramps, some space is created for the left directional ramps. Therefore, the interchange is called Inside Turning Left Interchange - ITL Interchange.
ITL Interchange should be used for four-way interchanges or other heavy traffic roads in order to increase the capacity and traffic safety at the crossing point.
ITL Interchange is suitable for interchanges where traffic is approximately evenly distributed in all traffic directions.
ITL Interchange has no conflict points.
It is less suitable for roads where most vehicles drive straight ahead and only a few vehicles turn right or left.
ITL Interchange left directional ramps are much shorter than all other known solutions for interchanges. The interchange is built in two levels.
These two facts significantly lower the cost of construction.
There is a comparison with other interchanges which also allow higher speeds for turning to the left and has no conflict point. This group includes: Stack Interchange, Turbine and Pinavia.
A comparison is also made for the interchange Cloverleaf. This interchange does not allow higher speed for turning to the left because all of the turns are headled by non-directional loop ramps. However, Cloverleaf is one of the cheapest options and it requires only one overpass.
The ramp with a horizontal radius of 250 m provides a driving speed of 80 km/h through the curve. At different interchanges, we have very different lengths
of ramps for turning to the left (L) and turning to the right (R):
Length of ramps for turning left and right (L/R):
Stack Interchange (L/R): 805 m / 390 m Turbina (L/R): 1295 m / 1070 m Pinavia (L/R): 1415 m / 680 m ITL Interchange (L/R): 395 m / 330 m
Length of all ramps at the interchange:
Stack Interchange: 9.980 m Turbina: 14.660 m Pinavia: 14.060 m ITL Interchange: 8.340 m
Length of all overpasses:
Stack Interchange: 3.320 m Turbina: 4.240 m Pinavia: 7.660 m ITL Interchange: 1.410m Option: 990 m overpasses and 420 m embankments
More technical data for each interchange and comparison with horizontal radiuses R = 250 m and R = 550 m:
Construction cost comparison has not been made because the price depends on the width of the ramps and the number of lanes.
The lengths of all ramps at other interchanges are 20-75% longer than in the ITL Interchange.
The lengths of all overpasses at other interchanges are from two to five times longer than in the ITL Interchange. In Stack-Interchange, the length of the overpasses is longer by the factor of 2.5, but it has a four-level construction.
A comparison is made for interchanges with horizontal radius of the left directional ramp 250 m. For larger radii and in a greater number of lanes, the price difference is even higher in favor of the ITL Interchange.
Overpasses incur the highest construction costs. In particular, the ITL Interchange is cheaper to build because it has a significantly lower length of overpasses than other interchanges. Maintenance is considered to be much cheaper.
A patent application was submitted to the Slovenian Intellectual Property Office and to the WIPO - World Intellectual Property Organization.
MSc. Goran Jovanovic, Ceng
Rafko Atelsek, BScEE