Temporary (summer) restrictions are in force since 1.7. for trucks and combination vehicles with a MPW of over 7.5t and trucks and special vehicles with trailers, if a MPW of the motor vehicle exceeds 3,5t.
Area: on motorways, trunk roads and 1stclass roads
Prohibition: from 1 July to 31 August·on Fridays from 17:00 to 21:00;·on Saturdays from 07:00 to 13:00;·on Sundays and public holidays from 13:00 to 22:00
Special prohibition: Vehicles concernedspecial motor vehicles and carts whose overall width exceeds 0.60m
Area: on 1stclass roads outside built-up areas
Prohibition: from 15 April to 30 September·on Fridays and the eve of a public holiday from 15:00 to 21:00;·on Saturdays and the first day of a series of public holidays from 07:00 to 11:00;·on Sundays and the last day of a series of public holidays from 15:00 to 21:00
More information you can find here