To solve the problem, we first define the number of seats in the smaller van as x. The larger van has 6 more seats than the smaller van, so it has x + 6 seats. The smaller van makes two trips, allowing it to transport 2x workers, while the larger van makes one trip, transporting y workers. The total capacity of both vans is given as 57 people, leading to the equation 2x + y = 57. Substituting y with x + 6 (from the relationship between the two vans), we get 2x + (x + 6) = 57. Simplifying this gives us 3x + 6 = 57, which leads to 3x = 51, and thus x = 17. Therefore, the smaller van has 17 seats, and the larger van, having 6 more seats, has 23 seats.