While Z-Drive can still be considered a "revolutionary" design trait of today's tugboats, engineers aren't resting on their laurels. New technical standards being introduced are testimony to designers' creativity and imagination; and the functionality is improved, as well. The use of tugs with either Z-drive or VSP propulsion have led to much faster, safer and more efficient ship-assist operations, without fail, says Robert Allan, of the marine engineering firm, Robert Allan Ltd. In fact, he adds, some tug companies with Z-drive tugs have had insurance premiums lowered because of the reduced risk of them damaging an attended ship with better tugs. But in no way have tugs evolved to their highest achievable level. The birth of such innovative designs was not unexpected, says Allan.