Understand use of dative in a construction containing "voraus"

Question

I translate the following

Andere Verkehrsträger sind in Sachen Innovation der Eisenbahn voraus.

as

Other forms of transport are more innovative than the railway.

I think that "die Eisenbahn" is used in the dative case here (could be genitive, but my gut feeling is it's more likely dative) but I don't understand why.

My thoughts so far:

1. This is not governed by the verb "sein" as both sides of "to be" are the subject, therefore nominative.
2. There is no preposition which demands the dative in this sentence - "voraus" is an adverb.
3. I can make an argument for "die Eisenbahn" being the indirect object: the railway is judged in comparison to other forms of transport. However, I would expect there to be a verb demanding the dative, but there isn't!
4. Perhaps "voraus" + dative is a fixed construction that I have not come across before? A quick google search didn't return any evidence to support this hypothesis.

I'd be really grateful for pointers to help me understand how the declination of "Eisenbahn" is determined in this example - thank you!

Answer 1

German has adjectives and adverbs governing a case. Most of them take dative.

Das hast du nun anderen voraus.

Er war ihr unterlegen.

Ich bleibe dir etwas schuldig.

Diese Erklärung war mir sehr nützlich.

Some take genitive.

Sei dir meiner Unterstützung sicher!

There are long lists of such adjectives, adverbs (and also participles, as you can see) but they are all incomplete. It's safe to assume free-floating datives and genitives in coupler phrases (and sometimes also with haben) have this function. The meaning is highly idiomatic anyways. A good dictionary will list those as e.g.

jdm. nützlich sein

along with the coupler used most often.

Answer 2

4) holds, whereby the construction is "X (entity) is/hat etwas voraus DAT-Y (entity)". This serves the purpose of comparison, as you note in 3). Although this construction does not exist in English with adverbs, it reminds remotely of adjectival constructions such as "x is preferable to y", where "to" covers the same dative function. See also "similar to".