Notation 
Explanation 
Example 
Meaning 
Remarks 
Applicable to the syntax column only: 
(.) 
For administration only 
(B)1 
Number B1, but on signposts only '1' appears 
In the syntax column and the system explanation: 
[..] 
variable string 
[2468] 
2, 4, 6 or 8 
[..] 
digit or letter range 
[24] 
2, 3 or 4 
A dash has to be taken literally if it is used in a different context than a range. 
.. 
numerical range 
A132931 
A1329, A1330 and A1331 
{.} 
optional string 
{[ab]} 
Optional letter a or b 
.. 
separator for variables consisting of more than one character 
[09][RDLN] 
A digit followed by either RD or LN 
Also used between { } brackets 
<..> 
amount of times 
[09]<12> 
1 or 2 digits 
^ 
superscript 
[09]<12>^a 
1 or 2 digits with superscript suffix a 
'.' 
literal (for special characters []{}<>();*) 
'('M')' 
Literal string '(M)' 
`.` 
reference to object defined somewhere else 
`suffix` 
reference to suffix 
; 
list separator (can also be used between brackets) 
M1;M2 
Numbers M1 and M2 
In the system explanation only: 
* 
any number of times 
[09]* 
any number of digits 
.d 
number of digits 
3d 
3digit numbers 
x,y,z,u,v 
digit variables 
xxy 
3digit number of which the first two digits are the same 
depending on context 
number variables 
CRx 
CR followed by some number 
(.) 
single digit separation 
x(x+1) 
12, 23, 34 etc. 
ord(.) 
ordinal function for letters 
ordinal number for letters in the standard Roman alphabet, e.g. ord(A)=1, ord(B)=2, ord(K)=11. For two of the same letters, numbering continues after 26, e.g. ord(AA)=27, ord(AE)=31. Also, ord(AAA)=53 etc. 
Numbers can not begin with 0, unless this is mentioned explicitly ('trailing zeroes'). 




More complicated examples: 
A[24][09]<12> 
A number with 2 or 3 digits beginning with 2, 3 or 4 
r10[19] 
Italicised numbers r101r109 (r is never used as a variable) 
A[09]<14>{'('M')'} 
A numbers with 1 to 4 digits and an optional suffix '(M)' 
B[15][09]<2>{[az]<12>} 
3digit B numbers beginning with 1, 2, 3, 4 or 5 and an optional 1 or 2letter (lowercase) suffix 
[AF][AC][09]<2> 
Two capital letters of which the first is AF and the second is A, B or C and two digits 
x(x+1)[18] 
Numbers of the form 121, 122, ..., 128, 231, 232, ..., 238 etc. 
[NS][09]<2>[RDLN] 
N or S followed by two digits followed by RD or LN (note that [RDLN] would mean R, D, L or N, while [RDLN] means either RD or LN) 
FR[09]<24>{[AT][01]} 
FR followed by 2 to 4 digits possibly followed by a letter A, B, ... or T or a dash and a 0 or 1 
Colours 
yellow 
Information not very reliable 
red 
Pure guess 
Order of road classes: Road classes are ordered in decreasing importance, where the following factors are taken into account (in decreasing order of prominence):
 Size of the administrative unit to which they are subordinate
For example, E roads are considered more important than national numbers, since Europe is larger than a country in Europe. Important note: the administration and maintenance of a road system can be independent of the area in which the numbers are unique. For example, Secondary state highways numbers in North Carolina are numbered per county (i.e. the same number appears in several countries). On the other hand, E roads are maintained by the countries, not by the EU. The area in which a number is unique is decisive here.
 Average length of roads
This criterion is usually highly correlated with the first one.
 Road standard
Examples: Motorways are more important than other dual carriageways, and paved roads are considered more important than unpaved roads. 
Country abbreviations: Though internet country codes (TLD codes) are becoming more and more popular, the International license plate codes are still much more common, especially in the world of road transport. Therefore this site uses these one to threeletter codes.
