Test and Technology Center Immendingen: Systematic torture: the test and assessment stretches

Oct 31, 2019

There are more than 30 test and assessment stretches covering a total area of 520 hectares. These allow a very wide range of situations to be simulated, for example complex traffic situations at inner-city junctions, driving on bumpy, cobbled surfaces or negotiating pass roads. The new acoustic test track has a surface layer with a precisely defined friction coefficient. Alongside acoustic testing, this also allows acoustic measurements to be carried out for certification purposes. Here is an overview of the most important modules by compass direction.

In the west

  • The Bertha area measuring 100,000 square metres is the largest asphalted area along with the handling dynamics area. 'Bertha' is a German acronym for 'test and assessment area for highly automated vehicles'. Assistance systems and automated driving functions can be tested on this 950-metre long and up to 650-metre wide surface. For example, the Bertha area makes it possible to test safety-relevant situations at motorway speeds, or merging/lane-changing situations at entries, and to verify collision prevention functions in convoy and crossing traffic. Driving tests are coordinated from the Bertha control center. Stationary and moving mock-ups of cars, pedestrians and two-wheeled road users, what are known as soft targets, enable assistance systems to be tested realistically. Automated testing allows test programmes with safety-critical manoeuvres to be absolved in an enclosed area with maximum precision. In the near future, these manoeuvres will also become possible for driverless vehicles with corresponding safety precautions and radio communication.

  • The handling dynamics area allows vehicle behaviour to be tested at the physical limits. The centerpiece of the asphalted area is a circle with a diameter of 260 metres.

  • Alpine conditions with a gradient of up to 16 percent and hairpin-like bend radii characterise
    the pass road.

  • The braking surface has five parallel strips with surfaces with different coefficients of friction – from asphalt and tarmac to tiles, which are particularly slippery in the wet. Braking measurements are carried out on this area, which can also be sprayed with water. The approach is long enough for even low-powered vehicles to be brought up to test speeds.

  • The 4x4 module is a topographically very varied, almost natural area with a network of gravelled roads and open areas for the testing and development of all-wheel drive and off-road vehicles. Even today, many regions of the world do not have metalled roads. The module includes two tracks with a 40-percent and 70-percent gradient for 30 metres, an inclined track and a demanding trial circuit. Before leaving the module, heavily soiled areas of the vehicle can be cleaned in the module's own carwash.

In the north

  • The inner city module has 1.5 kilometres of city roads with various junction layouts to test driving assistance systems, car-to-X communication and automated driving under real conditions. It is possible to simulate how vehicles in automated mode communicate with each other, for example.
  • To test automated parking procedures, a dedicated multi-storey carpark was constructed on the site next to the inner-city area. This has narrow ramps and reinforced concrete ceilings to test whether the vehicle can obtain the necessary GPS signals from satellites to search for a parking space. The test facilities also include parking surfaces with a wide range of markings and substrates.

  • Tests involving oncoming traffic are possible on the city road. Apart from lay-bys for test programmes involving stop & go traffic, the circuit also has roundabouts. The city road also has a two-lane dead-end with a turning bay.

  • The topography of the Test and Technology Center makes it possible to replicate steep uphill gradients such as those found in the Swabian Alb region, so that in future, many test runs can be relocated from the public roads to the Test and Technology Center. The two hill roads are winding two-lane country roads with major uphill and downhill gradients, and are designed for speeds up to 100 km/h (reduced on bends).

  • Seven different gradient stretches allow e.g. moving-off uphill to be tested under demanding conditions: the gradient is up to 100 percent, and the surfaces can be sprayed with water and have special features such as tiles or rollers. Cold-storage containers directly before the gradients allow cold-starting tests followed by a high power requirement.

  • The asphalt layer of the acoustic test track has a coefficient of friction precisely defined by standards ISO 362 and ISO 10844. Alongside acoustic testing, this also allows acoustic measurements to be carried out for certification purposes. Bays on the edge of the test track provide spaces for microphones.

In the east

  • The oval circuit is the centerpiece of the test center. Thanks to the banked curves, the four-kilometre long circuit can be negotiated at certain speeds without steering the vehicle. This "infinite straight" enables motorway journeys to be simulated – which is also important for the development of automated vehicles. One of the two straights can be sprayed with water, allowing the vehicles to be tested for dynamic waterproofing, i.e. water tightness when on the move.

  • The asphalted handling circuit with numerous bends (overall length 4.7 kilometres), which resembles sections of the Nürburgring circuit owing to the differences in altitude (31 metres), lies within the oval circuit. This is where high rates of longitudinal and lateral acceleration are achieved, so as to assess tyre and steering characteristics. Possible emergency situations that can occur unexpectedly at any time are also simulated – for example a sudden obstacle during motorway driving.

  • The wet handling circuit, which is likewise within the oval circuit, has a spraying system that allows a defined film of water to be achieved.

  • Comfort characteristics, noise and ground clearance can be tested in the comfort modules. To this end they have special surfaces such as cobblestones with or without potholes, sections with surface waves and kerb-mounting areas. The rigidity of vehicle bodies can be tested on torsion tracks and inclines. The gravel noise measuring stretch is a special feature. This has a gritted surface, allowing the reproducible assessment of noises caused by stones or grit in the wheel arches. 

In the south

  • The rough track and soiling stretch is a winding, farmtrack-like circuit with a special gravel covering of limestone marl and limestone grit. This surface material accumulates in gaps and joints – e.g. the axle bearings or the axle connections to the body. This allows countermeasures to be identified for day-to-day operations. To ensure that this soiling always has the same, reproducible quality, the 1.2-kilometre long circuit must be continuously maintained. Guard rails installed at ground level border the sides of the stretch. Depending on the test, a drying hall can also be driven through. Before the vehicles drive back onto a country road, the soiling must be substantially removed in a special carwash.

  • The four-metre wide farmtrack mainly follows the perimeter fence of the test site, and has a length of 7.1 kilometres. In some areas the gradient is between 15 and 20 percent.

  • The highway straight consists of two parallel straights plus turning loops, and is a motorway-like, two-lane stretch. This is where longitudinal dynamic and braking tests are conducted. A cross-wind system with large turbines is planned.

  • The country road is around 12 kilometres long, with two lanes in each direction. It is configured to provide over one dozen suspension testing possibilities, for example damping behaviour. It also includes a brow and a dip where the vehicle suspension is compressed and rebounds.

The Technology Center is partially accommodated in the former barracks. It has workplaces for employees working in research & development, plus logistics and storage areas and all the supply facilities for vehicle maintenance (workshops, wheel center, filling station, e-charging points).

As little noise and as much safety as possible: operation of the TTC

The operating times depend on the proximity to Immendingen and the type of test. For example, endurance tests on the oval circuit are possible around the clock, while in numerous other modules such as the Bertha area, vehicles are only tested from 6 a.m. to 10 p.m..

Employees in the control center monitor operations much like air traffic controllers. The test drivers have to undergo training for the individual modules. There is an on-board unit (OBU) in every test vehicle. This gives only authorised drivers access to the individual modules. The control center is in radio contact with all test drivers via its own LTE network[1]. The registered test vehicles are visible as green dots on the monitors in the control center. If an OBU has not been logged-in, the colour of the dot changes and the control center can investigate. A collision warning system integrated into the OBU also helps to prevent the test vehicles from approaching each other too closely.

Firefighting and rescue vehicles are ready for action around the clock on the test site. Double guard rails, stacks of tyres and crash zones ensure enhanced safety when performin

[1] Long Term Evolution, mobile radio standard with high transmission speed