Application Express :: How To Assign Concatenated Output To Item On Page Load

I have a table that reads something like this

City Route
NewYork 2
NewYork 4
NewYork 5
London A
London B
Paris X1

I want to assign Routes (concatenated) to an item on page load... as an example for NewYork it should read like this

P2_ROUTE = 2, 4, 5

I am looking to do the above using query, something like this

select (concatenated route)
from Table_A
where
City = :P2_City

how to concatenate variables.?