(a) Extreme temperatures. For vehicles required to be tested at extreme temperatures, the test sequence described in §610.41 will be performed using either test track or dynamometer, in ambient temperatures outside the 60° to 90° range specified in §610.64 as determined by the Administrator. The driveability tests described in §610.62 may also be performed at non-standard temperatures, as determined to be necessary by the Administrator.

(b) High altitudes. Vehicles required to be tested at high altitudes will undergo the tests described in §610.43 if necessary, on either test track or dynamometer as determined by the Administrator. One test location, at an elevation of no less than 4000 feet, will be selected.