When planning to drive through Germany, what speed does the navigation system use for limitless highways?

What is “the navigation system” for you? You need to specifiy the navigation system, because different navigation systems might have different default values.

I am a German and using 3 navigation systems in my car my experience is, that they assume 130 km/h for limitless highways. This is according to the “Richtgeschwindigkeit” a suggestion from the Federal Ministry of Transport and Digital Infrastructure which recommends to drive 130km/h on limitless highways (please not, this is only a suggestion from the Ministry, not the maximum allowed speed)

Forget navigation, from my driving experience you can assume a straight 100 km/h to get a good estimate.

The thing is what I call speed paradox: The slow parts of the trip are dominating the average speed, so fast driving does not reduce the travel time as much as you think.

Let’s say we drive 120 km (US citizens can half all values and replace them with miles). A 60 km section has road construction, so this part has a maximum speed of 80 km/h, otherwise you have unlimited speed and you are
driving the remaining 60 km with 160 km/h.

If you estimate it, you would think something like one part is 80 km/h and the other part is 160 km/h, so I will drive on average the middle speed, 120 km/h.

But the real average speed is: 45 min for the 60 km with 80 km/h, 22,5 min for the 60 km with 160 km/h. So the average speed is 120 km / 67,5 min ~ 107 km/h.

If you try to drive faster to increase the average speed, the result is:

180 km/h = 20 min => Av: 110 km/h
200 km/h = 18 min => Av: 114 km/h
240 km/h = 15 min => Av: 120 km/h

Even if you drive ridiculously fast you wont’t be able to increase the average speed much.

Add

• parts where the speed is shortly reduced: road work, dangerous spot etc.
• you need to take a few minute breaks for fuel and relaxing
• you need to overtake slower trucks from time to time

and your true average speed will drop under the perceived average speed to a good estimate of 100 km/h.

Looking in open source applications is one approach. OsmAnd is an application for Android that I’ve used in the past and has given fairly accurate ETAs. This was quite fruitless though, as the only thing I found was 40km/h applied when maxspeed is set to none (the standard way of tagging this, as an absent value might mean “unknown” or “not mapped yet”).

Testing OsmAnd by routing over a piece of highway that has maxspeed=none set for almost 40 kilometers, I get around 133km/h. An odd value, but the best estimate that I could make given multiple measurements (different parts of the same stretch). The application reports the estimated ascend and descend, but it’s hit and miss: if I see a relatively steep incline at point X and I route 3 kilometers before and after point X, it will suddenly not see the incline anymore. It also doesn’t seem to take this into account at all.

OSRM, another routing engine for OpenStreetMap has 140km/h coded in. Testing this service via the interface at openstreetmap.org however, I find that it reports speeds of around 115km/h ±2. At this point I’ve given up on deep-dives into source code.

Mapzen, also through the openstreetmap.org interface, gives me 105km/h ±1.

GraphHopper, also through the openstreetmap.org interface, gives me 120km/h ±0.003. Finally one that is consistent and makes sense.

YourNavigation, which seems to use Gosmore as the routing engine (operating on OpenStreetMap data), gives me 108km/h ±1. I get the feeling it’s one of the older, less-maintained services and it appears to be an outlier in terms of speed.

Google Maps simply does not compute. At 04:30 in the morning, it cannot make up its mind about whether I’ll take 8 or 12 minutes to do 15.8km. Hence the speed estimates are between 80km/h and 118km/h at 04:30 in the morning. I’d advise caution when using Google Maps to estimate your ETA and rather use another, more sane service that does not rely 100% on algorithms and 0% on sense.

Bing Maps seems to calculate with 130-135km/h, using its “without traffic” estimate. Currently (15:00 in Germany) it reports “light traffic” on this stretch, which brings the speed down to 115km/h.

Waze also takes traffic into account and has no option to turn it off. The results are quite varied/unreliable, though not as bad as Google’s: between 105.6km/h and 125.2km/h at 04:30AM (across 7 tests: all subsets of the same stretch of highway as I tested the previous services with). Again, use common sense, because at 04:30 you’ll not suddenly get stuck in 105km/h traffic for 19km, especially when an overlapping stretch of 18km drives 121km/h. (For the Americans, 105-121km/h is is 65-75mph.)

Conclusion

It depends. Some services estimate around 110-115km/h, and others assume you’ll reach the advisory speed in Germany of 130km/h.

In the past I’ve had good results with OsmAnd which is on the 115km/h side, so I suppose there is something to say for accounting some 10% of variance in traffic, curves, etc.

For services that try to take current traffic into account, make sure to apply common sense.