of the tank log-by-log, with the weight dragging further logs from the top. Logs were robust, each,14 ft long by 27in. diameter linked with 2in. wire rope. This proved a challenge to load, and Log Carpet AVREs had to be driven into a pit to enable the logs to be loaded at ground-level. Log Carpet could also be fitted to the unit's LVT4 Buffalo amphibious vehicles, and was particularly effective on waterlogged ground. Class 30 and Class 60 Trackways were later developments in the 1960s following extensive cold-war exercises in Germany, similar to Roly-Poly. Bridging and gap clearance During World War II, the AVRE was provided with a platform allowing a fascine to be carried on the vehicle front while the turret was traversed through 90 degrees. This could be released from within the vehicle to drop into gaps and ditches, allowing tanks (commencing with the AVRE itself) to cross, or angle up and over a ridge. AVRE's could also be modified with mounts and supports to carry a ready-assembled Small Box Girder Bridge from the front glacis plate. This could be dropped over gaps similar to traditional engineer bridging, or used to provide a ramp over a wall. Later, a towed version of the Small Box Girder Bridge was also developed, and was able to traverse a Bailey bridge for gaps further along the assault. A 60 ft section of Bailey bridge could also be pushed as the "Skid Bailey", with the leading sections raised slightly by winch to overcome obstacles. This allowed larger gaps to be breached. Trials and training were also conducted with the Bailey Mobile Bridge, providing 150 ft of bridge articulated on tracks at the centre, and the Brown Bailey, carrying 140 ft of Bailey bridge between two tanks, the rear AVRE launching the bridge over rollers on the front vehicle. Post-war a Folding Small Box Girder Bridge was also developed, articulating in the middle. AVRE bridging can be distinguished from the Armoured Ramp Carrier (ARK) by both purpose and operator. AVRE bridges leverage the AVRE to enable Royal Engineers to more safely accomplish traditional bridging activities where an ARK may not be appropriate. The ARK is intended to rapidly deploy a ramp or smaller gap bridge without the need for specialised engineering skillset, simply by driving into it. An AVRE deployed fascine could be used to raise the front of the ARK if needed,