The STRABAG subsidiary KAB Straßensanierung dares a premiere: the use of a 3D-controlled milling machine for the rehabilitation of a motorway section. Technological innovation meets proven expertise. A site visit.

The S33 near Sankt Pölten, Austria – instead of the thousands of vehicles that typically race across the carriageway every day, a milling machine is eating its way through the asphalt surface on this June morning. The milling bits hammer loudly into the old road; bitumen and rock become visible, supported by a protective fleece, with only gravel underneath. Such gruelling work means that eight hundred bits are worn out every day.  

Construction machine with digital update – the use of a 3D-controlled asphalt milling machine reduces the workload of the construction site team: the machines are no longer adjusted by hand; instead, they work completely automatically.

A few metres further up, on the operator’s stand, the machine operator looks at several screens. They show figures and a digital image of the construction site. Today, for the first time, a new digital technology is being used here: the so-called SmoothRide system. The application was developed by Topcon, a company specialising in geopositioning and machine control. It enables continuous measurement of the actual values via the side plates of the milling machine. By comparing the actual values with the target values from the 3D model, the precise milling depth can be controlled automatically.  

The STRABAG subsidiary KAB has been working in partnership with Topcon and Wirtgen, the leading manufacturer of milling machines, for many years. Together, they test new developments under practical conditions – like the 3D milling machine in this pilot project on the S33.  

The first step is to use a digital scanner to record the entire road surface. In what’s called mobile mapping, the scanner is mounted on a car that drives along the road at speeds of up to 80 km/h and measures the three-kilometre stretch of road. The STRABAG team needed about an hour to measure the three-kilometre test section on the S33. It’s a remarkable speed, as the comparison shows: Typically for this stretch, two to three people would be busy for several days, measuring cross-sections by hand at regular intervals. In most cases, the motorway may even need to be closed off on one side.  

Accurate to the millimetre – the machine operator controls the work of the 3D-controlled milling machine via screen. 

High-precision image

Die neue Technologie liefert nun ein um-fassendes und hochpräzises Bild der bestehenden Fahrbahnoberfläche. Der Scan wird mit den Planungsdaten der Auftraggeberseite abgeglichen. Die finale Planung erfolgt dann mit dem Ziel einer verbesserten Ebenheit der Fahrbahn. Mit diesen Daten lässt sich ein 3D-Modell für das Fräsen erstellen. Die Frästiefen müssen auf dem Fahrbahnbelag nicht mehr angezeichnet werden, sondern werden automatisch gesteuert. Auch die Menge des Fräsguts kann vorab exak

This new technology provides a comprehensive and highly precise image of the existing road surface. The scan is compared with the client’s planning data to establish how to best improve the evenness of the road surface. With this data, a 3D model can be created for milling. The milling depths no longer have to be marked on the road surface, but are controlled automatically. The amount of milled material can also be precisely determined in advance, along with how many trucks will be needed to remove the old material, for example.  

For the machine operators on-site, the new technology improves safety, because they no longer have to lean out of the operator’s stand or climb down to take manual measurements, which increases the risk of accidents. “The only disadvantage“, says KAB fleet manager Klaus Palle, “is that the scanner and the 3D machine control do not work in subways and tunnels because there’s no GPS signal there.“ This is something they will address together with their partner Topcon.  

“For our Cold Milling Division, we already tested the first telematics solutions on the market years ago, together with STRABAG. This partnership is very beneficial, because we get feedback directly from the experts on the construction sites. This critical and in-depth technical feedback, this eye-level exchange with the very users who operate these devices on a daily basis, is invaluable to our progress in product development.“  

Boris Galic
Product Manager and Key Account Manager, Wirtgen Group.

The Wirtgen Group is one of the largest manufacturers of cold milling machines in the construction machinery industry.  

“We work with 3D models, so data is of fundamental importance to us – the better the data, the better we can plan with it and ultimately build a road. Perhaps this comparison illustrates how precisely we work: our mobile phone locates us with an accuracy of about three metres. In contrast, the position of the milling machine is determined in the centimetre range.“

Christoph Bertsch
Business Development Manager Paving EMEA, Topcon.

Topcon Deutschland Positioning GmbH is one of the leading providers of positioning solutions for the construction industry.
See here the use of the 3D-controlled asphalt milling machine on the S33 near Sankt Pölten. (German only)
“The technologies are often still in their infancy”.
Klaus Palle
KAB Straßensanierung GmbH & Co KG
Design & Engineering
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