Indication of B numbers on motorways in Germany
Last updated 6-7-2019, fixed links 9-3-2024
Contents
B numbers on motorway signs
Normally, federal highway (B) numbers are indicated at exits on motorways, but in many cases they are missing.
The B31 and B311 at exit Geisingen ion the A81.
This differs per federal state. Three states (Berlin, Brandenburg and Mecklenburg-Vorpommern) score a full 100 %: numbers are always indicated. In Baden-Württemberg, the score is only about 60 %. The overall average is 85.8 %.
In Bayern, B numbers were never indicated on motorways untial around 1990. There was one exception: the B2 at exit Roth on the A6.
Rules and method
Data points
One data point is the indication or absence of a B number at a given exit in one direction. To illustrate this, consider the fictitious A50 with an exit to the B1 and B2 from both directions, the B1 only goes north and the B2 both ways.
A fictitious example
This gives rise to 4 data points: indication of the B1 from the west and from the east, and the same for the B2. We do not distinguish between the B2 north and southbound because in most situations the split occurs only after leacing the motorway.
Data collection
Various pictures from the internet were used plus Google Streetview and the Autobahn Information System (AIS).
The total number of data points is 2002. This covers almost all cases in the country.
Indirect references are also counted as indicated numbers, but never counted as missing.
Changes
When a road number is rerouted or downgraded, it usually takes some time until signs are changed. For changes a 10 year grace period is applied. For example, the B483 at Wuppertal-Langerfeld on the A1 is not counted as missing because it has only been there since 2015.
The B209 was rerouted to exit Fallingbostel on the A7 but in 2018 it still did not appear on signs there. Obsolete numbers sometimes also remain on signs. Some old situations based on old pictures which were later changed are included.
Which signs
Normally the numbers appear 3 times: at the advance directional sign (most often at 500 m before the exit), at the exit, and on the off ramp after leaving the motorway. To be counted as indicated, a number must appear eithrt on the advance directional sign or at the exit, or both. As an exception, if the number is clearly visible from the main carriageway on a sign on the ramp at a point where one can still take the exit, it is counted as indicated.
Borderline case: At exit Offenburg of the A5, the number 33a is visible on the ramp sign.
Overview
B number sub classes
We consider three sub classes:
The B numbers under 140 are the main highways introduced in 1934 (originally in 1932 but those were not signposted and many were changed in 1934).
Numbers up to 330 were the less important roads introduced before World War II.
Higher numbers appeared from the 1960s, only in West Germany, and in the former GDR they do not exist until today.
Are the more important numbers indicated better on signs? At first sight it seems that the lowest class of numbers over 330 score slightly lower (82.6 %) than the other classes, but this is mainly due to the fact that the federal states in the former GDR indicate the numbers much better than in the west, and the higher numbers do not exist there, so the average score for the highest numbers is lower because it is only composed of scores from former West Germany. Looking at individual states, we see that for example in Niedersachsen and Nordrhein-Westfalen, the higher numbers are even indicated better than the lower numbers. The difference is small though, and most probably just coincidence. However, in Baden-Württemberg, the higher numbers are indicated only in less than 40 % of cases.
Two directions at the same exit
As can be expected, if a number is indicated in one direction, and the same road can be reached from the other direction, the conditional probability that it is also indcated in that direction is higher than the average. The probability that it is not indicated is roughly half of that in the general case.
Dependence on other roads
It is also not surprising that the presence of another B number at the given exit has an influence on the probability that it is indicated. When there are two numbers, often only one of the two is indicated and the other one is forgotten or deliberately omitted. Thus the numbers only appear in 78.7 % of cases, compared to the overall success percentage of 85.8. There are only a handful of cases where an exit gives access to three B roads: two in Bayern, one in Niedersachsen and one (only in one direction) in Sachsen, thus giving only 21 data points, and by coincidence the success percentage is roughly the same as the overall percentage.