Select longest continuous sequence

I am trying to construct a query in PostgreSQL 9.0 that gets the longest sequence of continuous rows for a specific column. Consider the following table: lap_id (serial), lap_no (int), car_type (enum), race_id (int FK) Where lap_no is unique for each (race_id, car_type). I would like the query to produce the longest sequence for a given race_id and car_type, so it would return an int (or long) that is highest. With the following data: 1, 1, red, 1 2, 2, red, 1 3, 3, red, 1 4, 4, red, 1 5, 1, blue, 1 6, 5, red, 1 7, 2, blue, 1 8, 1, green, 1 For car_type = red and race_id = 1 the query would return 5 as the longest sequence of the lap_no field. I found a similar question here however my situation is a bit more straightforward. (I would also like to know the longest sequence for a given car_type for all races, but was planning to work that out myself.)