Heavy Duty trucks demand heavy duty loads, these trailers are here to provide that extra size to fit the bill.
The fluid trailer is a modified version of the standard fluid trailer, which has been given another axle and buffed suspension stiffness. It still can't handle 100% fill level, but it can safely go above the previous 75% cap I had in place. However, you can test the limits at your own discretion, since 75% is still a lot of fluid and weight (nearly 75 000 kg of weight if filled with water).
The Dryvan trailer is a more heavily modified version of the standard Dryvan trailer, the swinging doors have been replaced with a single ramp, and the interior height has been increased. The length has also been increased, now much longer than standard. It has also inherited the tri-axle set-up and buffed suspension. Though it may not look it from the thumbnail, the semi truck can actually fit inside the trailer (at least width wise), so it should have plenty of space for a couple of cars and trucks.