What was once the largest roundabout in all of Germany, the Offenbacher Kaiserlei roundabout on the border with Frankfurt, is history.

The final phase of the massive renovation project has begun.

The work that will remove the roundabout that was put into operation in 1965 and replace it with a significantly more efficient and safer traffic route is to be completed this summer, as the Offenbach planning department head Paul-Gerhard Weiß (FDP) announced on Thursday.

Jochen Remert

Airport editor and correspondent Rhein-Main-Süd.

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In the meantime, the flow of traffic from Frankfurt to Offenbach and vice versa, as well as the traffic via the radiant mountain road to the Autobahn 661 and from it in the direction of the city, have been diverted and run on new ramps, bridge elements and routes.

The resulting intersections of the individual routes are monitored with the help of sensors and cameras, a computer is able to control the traffic depending on the volume via the traffic light system.

With this and with the separation of the traffic between Frankfurt and Offenbach from the national traffic on the A 661, one is now much better prepared for the future development of traffic flows.

“Surprises” underground

The fundamental redesign of the area also required extensive underground work.

This has also opened up the possibility of laying a number of new lines on behalf of utilities and thus promoting further development of the commercial area on the Kaiserlei.

According to the information, the underground also had some “surprises” in store.

Not only did a number of concrete piles have to be driven deep into the ground.

The civil engineers also repeatedly came across lines that were not listed anywhere, including an old, 300-meter-long steam line that was coated with asbestos and had to be disposed of at great expense.

According to Weiß, these uncertainties and the enormous price increase in the construction sector are the main reasons why the magistrate is now assuming a cost volume of 60 million euros.

This now includes around 7.5 million euros in additional costs.

However, according to Weiß, the total volume can still be reduced by additional claims against various contractors by millions.

According to the current status, however, the share that the city of Offenbach has to bear itself has increased by two to ten million euros, with a part being borne by the utilities whose lines were laid during the course of the work.

Irrespective of this, the project will certainly be significantly more expensive than assumed at the start of the project in 2017.

At that time, the estimates were around 40 million euros.

The second major project that Offenbach is currently tackling is the conversion of the market square in the city centre.

Although the investment volume is significantly lower than at the Kaiserlei, price increases in the construction sector, delays due to supply bottlenecks and unforeseeable obstacles underground, such as unmarked lines and building remains, also led to an increase in costs.

As a result, 83,000 euros more had to be paid for the services of the engineering office, which took over the entire execution planning of the market square conversion for the city.

For all these reasons, according to Weiß, the project budget for the conversion had to be increased by two to 7.5 million euros.

In this case, too, it is possible to reduce the costs through the city's management of additional claims against contractors.