Bulk trailers take on a number of forms. Rigid trucks with a tipping bed can be used without a trailer, but transport a limited volume. These trucks are compelled to wait during the loading process, but are agile on poor forest roads and have a short unloading time. For longer chip transport, semi-trailers fitted with reciprocating slatted floors, such as the Walking Floor™ trailer, or side tilting designs, can be used successfully. Articulated trucks can have problems on winding or steep roads, but benefit greatly from their superior load capacity. Semi-trailers and drawbar trailers can be exchanged at the landing, or the truck can wait to be filled. This requires matching with a high production chipper. Side-tipping trailers have minimal offloading times, but require specialized receiving bunkers that run the entire length of the trailer. End-loading trailers can unload into more commonly available bunkers. Chipper-trucks (fitted with own chipper) have reduced transport capacity but have high mobility in that they are not dependent on other machines and work well in areas with a higher number of smaller landings.