Features + advantages

  • Active and intelligent trailer steering
  • Complete directional stability on bends and in tight spaces
  • Track-in-track mode: the self-steering trailer follows the exact track of the truck
  • Easy manoeuvring: reverses like a semi-trailer
  • Direct and fast steering action
  • Manual steering possible but is only required in extreme situations
  • No self-steering trailer swerving
  • Low wear on tyres, steering system and bearings
Made in Germany. Since 1878.

Many manufacturers talk about quality and a long service life. We actually deliver it.

With each new vehicle generation, we raise the bar a little higher – to achieve things that our competitors have not. True DOLL quality is all about usefulness; it's about satisfaction, being ahead of your game, taking pride in what you do. And it's about reliability and safety. Our quality sets the standard – mile after mile, on any terrain.


The best DOLL innovation for 25 years. The systems, functions and speeds are all logical and co-ordinated.

Jonas Körner, Managing Director, Raimund Körner Holztransporte

DOLL ratioplus – the steering system of the future

Characteristics of ratioplus technology

Extraordinary stability

The electronic stability program prevents accidents by identifying the potential for self-steering trailers to swerve at an early stage and automatically applying the bolster brake.

Automatic track adjustment

Whether you're negotiating a bend or driving on a straight road, you can automatically adjust the self-steering trailer track at the touch of a button in any situation. The system also activates automatically at speeds of over 40 km/h.

Hydraulic bolster lock as standard

Conveniently operated from the crane, the hydraulic bolster lock is a helpful tool during loading and unloading.

Key data at a glance

You can check the axle loads, the current total weight and the current bolster distance centrally from the crane or the driver's cab.

Simple hitching

The hydraulic winch makes the self-steering trailer easy to pull in. You define your own optimum end point in the system.

Switch driving programs at the touch of a button

It's quick and easy to switch between the three intelligent programs: self-steering, track-in-track and reversing. Operation is completely intuitive, depending on the driving situation.