The sentence

#HAS A TRIVIAL ERROR, PERHAPS JUST A TYPO

It's just that simple. the two "of"s were meant to be "are" (or "is").

"of" is utterly meaningless, might as well have typed "cat" there.

The total length of the public road's network is 29151 km, out of which 1243 km are motorways, 6810 km of national roads and 21098 km of regional and local.

should be..

The total length of the public road network is 29151 km, out of which 1243 km are motorways, 6810 km are national roads, and 21098 km are regional and local roads.

or, if you prefer,

The total length of the public road network is 29151 km, out of which 1243 km is motorway, 6810 km is national road, and 21098 km is regional or local road.

It's truly incredible something so simple can get so much press here.

Regarding the issue asked about in the comment below.

It couldn't be simpler. You can interpret the three references as to "sections" (so for example, the first section discussed is a section 1243 kms long), in which case singular.

Or you can interpret the discussion as about the various "kilometer lengths of highway" in which case plural.

What's the question? It's the norm in English that there are at least three ways to go with anything. You can choose either the plural "way" or the singular "way"; this is totally unsurprising in English: it is the norm, there is nothing, whatsoever, to say about it. Just choose one or the other.

Note also the infuriating apostrophe-s in "road's" - idiotic, or just a typo.

The sentence

HAS A TRIVIAL ERROR, PERHAPS JUST A TYPO

It's just that simple. the two "of"s were meant to be "are" (or "is").

"of" is utterly meaningless, might as well have typed "cat" there.

The total length of the public road's network is 29151 km, out of which 1243 km are motorways, 6810 km of national roads and 21098 km of regional and local.

should be..

The total length of the public road network is 29151 km, out of which 1243 km are motorways, 6810 km are national roads, and 21098 km are regional and local roads.

or, if you prefer,

The total length of the public road network is 29151 km, out of which 1243 km is motorway, 6810 km is national road, and 21098 km is regional or local road.

It's truly incredible something so simple can get so much press here.

Regarding the issue asked about in the comment below.

It couldn't be simpler. You can interpret the three references as to "sections" (so for example, the first section discussed is a section 1243 kms long), in which case singular.

Or you can interpret the discussion as about the various "kilometer lengths of highway" in which case plural.

What's the question? It's the norm in English that there are at least three ways to go with anything. You can choose either the plural "way" or the singular "way"; this is totally unsurprising in English: it is the norm, there is nothing, whatsoever, to say about it. Just choose one or the other.

Note also the infuriating apostrophe-s in "road's" - idiotic, or just a typo.

The sentence

#HAS A TYPO

it's just that simple.

The total length of the public road's network is 29151 km, out of which 1243 km are motorways, 6810 km of national roads and 21098 km of regional and local.

should be..

The total length of the public road network is 29151 km, out of which 1243 km are motorways, 6810 km are national roads, and 21098 km are regional and local roads.

or, if you prefer,

The total length of the public road network is 29151 km, out of which 1243 km is motorway, 6810 km is national road, and 21098 km is regional or local road.

It's incredible something so simple can get so much press.

Regarding the issue asked about in the comment below.

It couldn't be simpler. You can interpret the three references as to "sections" (so for example, the first section discussed is a section 1243 kms long), in which case singular.

Or you can interpret the discussion as about the various "kilometer lengths of highway" in which case plural.

What's the question? It's the norm in English that there are at least three ways to go with anything; almost every sentence as given is wholly ambiguous without context.

Note also the infuriating apostrophe-s in "road's" which is just entirely poorly thought out.

The sentence

#HAS A TRIVIAL ERROR, PERHAPS JUST A TYPO

It's just that simple. the two "of"s were meant to be "are" (or "is").

"of" is utterly meaningless, might as well have typed "cat" there.

The total length of the public road's network is 29151 km, out of which 1243 km are motorways, 6810 km of national roads and 21098 km of regional and local.

should be..

The total length of the public road network is 29151 km, out of which 1243 km are motorways, 6810 km are national roads, and 21098 km are regional and local roads.

or, if you prefer,

The total length of the public road network is 29151 km, out of which 1243 km is motorway, 6810 km is national road, and 21098 km is regional or local road.

It's truly incredible something so simple can get so much press here.

Regarding the issue asked about in the comment below.

It couldn't be simpler. You can interpret the three references as to "sections" (so for example, the first section discussed is a section 1243 kms long), in which case singular.

Or you can interpret the discussion as about the various "kilometer lengths of highway" in which case plural.

What's the question? It's the norm in English that there are at least three ways to go with anything. You can choose either the plural "way" or the singular "way"; this is totally unsurprising in English: it is the norm, there is nothing, whatsoever, to say about it. Just choose one or the other.

Note also the infuriating apostrophe-s in "road's" - idiotic, or just a typo.

The sentence

#HAS A TYPO

it's just that simple.

The total length of the public road's network is 29151 km, out of which 1243 km are motorways, 6810 km of national roads and 21098 km of regional and local.

should be..

The total length of the public road network is 29151 km, out of which 1243 km are motorways, 6810 km are national roads, and 21098 km are regional and local roads.

or, if you prefer,

The total length of the public road network is 29151 km, out of which 1243 km is motorway, 6810 km is national road, and 21098 km is regional or local road.

It's incredible something so simple can get so much press.

Regarding the issue asked about in the comment below.

It couldn't be simpler. You can interpret the three references as to "sections" (so for example, the first section discussed is a section 1243kms long), in which case singular.

Or you can interpret the discussion as about the various "kilometer lengths of highway" in which case plural.

What's the question? It's the norm in English that there are at least three ways to go with anything; almost every sentence as given is wholly ambiguous without context.

Note also the infuriating apostrophe-s in "road's" which is just entirely poorly thought out.

The sentence

#HAS A TYPO

it's just that simple.

The total length of the public road's network is 29151 km, out of which 1243 km are motorways, 6810 km of national roads and 21098 km of regional and local.

should be..

The total length of the public road network is 29151 km, out of which 1243 km are motorways, 6810 km are national roads, and 21098 km are regional and local roads.

or, if you prefer,

The total length of the public road network is 29151 km, out of which 1243 km is motorway, 6810 km is national road, and 21098 km is regional or local road.

It's incredible something so simple can get so much press.

Regarding the issue asked about in the comment below.

It couldn't be simpler. You can interpret the three references as to "sections" (so for example, the first section discussed is a section 1243 kms long), in which case singular.

Or you can interpret the discussion as about the various "kilometer lengths of highway" in which case plural.

What's the question? It's the norm in English that there are at least three ways to go with anything; almost every sentence as given is wholly ambiguous without context.

Note also the infuriating apostrophe-s in "road's" which is just entirely poorly thought out.