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"Mehlaf" is a relatively new Hebrew word, designating an "Interchange" which is officially defined as a "multi-level crossroad". In the vernacular of the average driver, a Mehlaf means a multiple or bi-level road intersection.
Intersections of roads at different grades are through loop-ramps or straight sections called connectors.
Generally, interchanges (or Mehlafim) constitute a connection between a freeway and a main highway or between a main highway and a secondary road. The basic principles of the operation of an interchange are:
- Traffic crosses the freeways via bridges and their approaches.
- Access to the freeways is possible via special lanes permitting acceleration on joining and deceleration on leaving. The purpose of these lanes is to eliminate clashes between moving vehicles, diverging from or merging with freeway traffic.
- In order to minimise the chance of collisions on the freeway, the traffic flows must be separated.
- At junctions between secondary roads possible clashes are prevented by features such as traffic lights, road signs, markings etc.
The interchanges bring innovations of the 20th century to road construction technology and these make the cost even higher through the construction of bridges (sometimes elevated highways) and also as a result of occupying large areas of land.
Every type of interchange is known by a name characterising its geometrical design (see illustration).
The planning of a modern interchange requires a thorough knowledge of bridge, road, and traffic engineering, as well as allied branches such as those of environment, drainage and lighting etc. Only a close co-operation and co-ordination between engineers in these different fields can ensure the successful design of an interchange.
The first interchanges in the world were built at the end of the twenties in the USA and Europe. In this country, a small number of municipal interchanges (the Shell Bridge in Haifa and the Yehuda Hayamit Bridge in Yafo) were built in the days of the British Mandatory Government, but these are a far cry from the constructions we know today.
Israel built its first "trumpet" type interchange - the Zikhron Interchange - in 1967 near Zikhron Ya'akov within the framework of the construction of the Hadera-Haifa freeway. During the same period the "Pardo" type Rishon Interchange, near Rishon Le Ziyyon, was opened to traffic and at a later stage interchanges were built on the Hadera-Haifa road at Atlit and at the southern approaches to Haifa (Haifa South Interchange). Today, the Public Works Department, which is in charge of maintaining the inter-urban road network, maintains 19 interchanges.
The "Pardo" (4-quadrant) type Interchange, shown on the stamp, was completed in 1978 and constitutes a link between Highway No.4 (Morasha-Ashdod) - which, in accordance with the national master-plan, will remain a freeway [on the upper level] and Highway No.44 (Tel Aviv South-Ramla) [on the lower level]. This interchange carries a daily traffic volume of about 100,000 vehicles. It is located at the Ha-Shiv'a Intersection, which, despite the installation of traffic lights, had become a source of long queues and a safety hazard. The construction of the interchange has improved the safety factor, expanded the traffic capacity and eliminated the bottlenecks, permitting a steady flow of traffic.
The Ha-Shiv'a Interchange extends over an area of some 260 dunam near Moshav Mishmar Ha-Shiv'a which is dedicated to the memory of the seven Jewish Settlement Policemen who fell in the defence of the area and the road leading to Jerusalem.
