Gloom: some messages go to yahoo and some to google.
The correct move is to lock off posting to yahoo.

'only' is nearly always positioned wrongly.
The ellipsis resulting in 'Only trams' vs 'trams only' really stemmed from
'Only trams are allowed to enter'.
The stupid sign reads 'No entry trams only': Are trams the only things not
allowed to enter? Elephants are welcome.
That is in the league of 'No way trespassers will be prosecuted'.

'Only' has to sit with the restriction.
My usual example: I eat only bananas vs I only eat bananas.
The first restricts my diet to bananas; the second debars various other
actions possible with bananas.

Now to the one cited on yahoo TDU.
"He only drove tram 294 once" - still allows all sorts of other actions with
tram 294, although not as kinky as the ones with bananas.
"Only he drove tram 294 once" - meaningless. If he drove it once, and
everyone else drove it two or more times, it should read 'only he drove tram
294 only once'.
The spirit of the sentence was 'He drove tram 294 only once'.

Re bus lanes, go for a compound adjective: 'Bus-only lane'.

Roderick.

> "ONLY TRAMS", not "TRAMS ONLY".

Either is OK but the latter is better
> Another example: "ONLY BUS LANE", not "BUS LANE ONLY" (!)

Only the second. The first is nonsense.

"Only" can be an adjective and conjunction as well as an adverb.
Always putting it in front can produce different meanings. "He only drove
tram 294 once", is different to "Only he drove tram 294 once".
In the situation here though, "only" is being used as a synonym for "just".

So, "Just Trams" or "Only Trams" would work, whereas "Only Tram" or "Just
Tram" sounds awkward. Similarly for buses.
"Only bus lane" may be grammatically correct, but it is an abomination
seeking the "only bus" that can use it.

My understanding with the
way proper English should be spoken is that the adverb immediately precedes
the noun to which it is referring.
Ie "ONLY TRAMS", not "TRAMS ONLY".
Another example: "ONLY BUS LANE", not "BUS LANE ONLY" (!)

I can understand a sign such as "NO ENTRY - (TRAMS) EXCEPTED", but
what exactly would "NO ENTRY - (TRAMS) ONLY" mean.