would likely use vehicle motion simulation including cross wind conditions to determine margins relative to derailment and rollover. If the superelevation determined for a dedicated passenger route curve on regulatory and safety bases is below it may be desirable to increase the superelevation and reduced the cant deficiency. However, if on such a curve some trains regularly travel at low speeds, then raising the superelevation may be inadvisable for passenger comfort reasons. On a mixed traffic route owned by a freight rail company, freight considerations are likely to prevail. On a mixed traffic route owned by a passenger rail company some kind of compromise may be needed. Cant deficiency is generally looked at with respect to ideal track geometry. As geometry of real track is never perfect it may be desirable to supplement the static considerations laid out above with simulations of vehicle motion over measured geometries of actual tracks. Simulations are also desirable for understanding vehicle behaviour traversing spirals, turnouts, and other track segments where curvature changes with distance by design. Where simulations or measurements show non-ideal behaviour traversing traditional linear spirals, results can be improved by using advanced spirals. Good track geometry including advanced spirals is likely to foster passenger acceptance of higher CD values. United States For passenger traffic superelevations and authorized speeds can be set so that trains run with as much cant deficiency as is allowed, based on safety, on relevant regulations and on passenger comfort. As of 2007 the US Federal Railroad Administration regulations limit CD to for tilting passenger vehicles, for conventional vehicles. This FRA regulation is based on AAR standards based on a single study in the 1950s on a rail line in Connecticut. In Germany, where axle loads are typically lower than those in the USA, tilting trains are allowed to operate with CD in some cases. CD above can be considered too uncomfortable for passengers (e.g. things on tables might slide off), except for tilting trains. The FRA issued new information on cant deficiency in 2009 under FRA-2009-0036-0003. Due to the circumstances outlined, the federal regulations on cant deficiency were amended such that any rail vehicle may operate with up to 3 inches of cant deficiency and any vehicle that is to be operated above this number must be approved by the FRA for such operations. Approval is governed by conditions outlined in CFR chapter 49 section 213.329 part (d)