Smartbrake, The Industry Leader In Exhaust Brake Manufacture. Hersham Are Major Suppliers of Engine Brakes To The Fire Truck Industry. Smartbrake is Also widely used in School Buses And Of Course Heavy Trucks. For Many Years Hersham's Engine Brakes / Exhaust Brakes Have Been Fitted As Standard Equipment On Many Diesel Engines and O.E.M Production Lines. Hersham Has Over The Last 30 Years Seen Its Market Share Grow To The Point That it is Now Market Leader In This Field.