AddEventHandler('entityCreated', function(entity)
    -- not valid anymore?
    if not DoesEntityExist(entity) then return end 

    -- rest of core remains the same
    local entityType = GetEntityType(entity)

    -- not a vehicle? bail out
    if entityType ~= 2 then return end

    -- only for 'random' population cars
    if GetEntityPopulationType(entity) > 5 then return end

    -- if >0.5 (50% chance of locking), bail out
    if math.random() > 0.5 then return end

    -- lock!
    SetVehicleDoorsLocked(entity, 2)
end)