CREATE TABLE table_40899 ("Class" TEXT, "Type" TEXT, "Built" TEXT, "Number" FLOAT, "Withdrawn" FLOAT)

What is the sum of numbers that had a type of Driving Van Trailer?
SELECT SUM("Number") FROM table_40899 WHERE "Type" = 'driving van trailer'
SELECT SUM("Number") FROM "table_40899" WHERE "Type" = 'driving van trailer'