Guidelines

1. Vehicles sorting before the interchange
At a sufficient distance before the interchange on the highway (at least 1500 m), it is necessary to limit the speed and inform the drivers with the vertical and horizontal signaling which lane leads to which traffic direction. This also helps avoid unnecessary weaving within the interchange and prepare drivers for timely sorting.
The ITL Interchange is suitable where traffic is approximately evenly distributed in all directions. The inner lanes lead to left directional ramps. Vehicles that turn to the left do not change the lane. Vehicles driving straight or turning to the right, move to the right-hand lanes before the interchange.

Video presentation:

2. Level change of the slip road for turning to the left
Left directional ramp has to remain on the unchanged level until it crosses both of the left directional ramps at the opposite level. This length is about 2/3 of the entire length of the directional ramp. Therefore, there is a very short distance to pass to come to the opposite altitude level. Sharp vertical convex and concave curves allow significantly lower speeds than allowed by a horizontal turn. In order to mitigate vertical curves, we use a trick to slightly raise the level of both roads in the diagonal corners. In the other two diagonal corners, the level of the roads should be slightly lowered. The straight lane must also be adapted to these level changes.

Practical calculation has shown that a level rise of about 80 cm on one side and a level drop of about 80 cm on the other side is sufficient.
The schemes below shows the solutions.

Upper and Lower Left directional ramp Profilel

Schematic representation of levels

Video presentation:

Designing vertical slopes is very complex and challenging. If you are interested in workability or need help calculating, please contact us.

Project

Project documentation has been prepared, which shows the exact design of each directional ramp.

Project parameters:

• Radius of the horizontal circular curve for left directional ramps R = 250 m
• Vertical rounding with a convex radius of 4000 m and a concave radius of 3000 m
• Altitude difference between individual levels 6 m
• Permissible speeds 80 km/h

The project includes plans::

• Verical alignment - Lower straight directional ramp
• Verical alignment - Lower left directional ramp
• Verical alignment - Upper left directional ramp
• Horizontal alignment

See complete project:

Case Study

We made case studies for some existing interchanges. Instead of the existing interchanges, we placed ITL Interchange at the same location.

Europe:

United States of America: