Section 810.104 - Applicability of other provisions(a) Projects authorized under § 810.102 shall be deemed to be highway projects for all purposes of title 23 U.S.C., and shall be subject to all regulations of title 23 CFR.(b) Projects approved under this subpart on the Federal-aid Interstate System for exclusive or preferential high occupancy vehicle, truck, and emergency vehicle lanes are excepted from the minimum four-lane requirement of 23 U.S.C. 109(b) .(c) Exclusive or preferential lanes on the Interstate System, including approaches and directly related facilities, can be constructed with Interstate construction funds only if they were approved in the 1981 Interstate Cost Estimate.(d) The Federal proportional share of a project approved under this subpart shall be as provided in 23 U.S.C. 120 for the class of funds involved. The Federal share for Interstate substitution projects is 85 percent except for signalization projects which may be 100 percent as provided by 23 U.S.C. 120(d) . The provisions of section 120(d) title 23 U.S.C. may also be applied to regularly funded projects under § 810.102 of this subpart as follows:(1) Signalization projects.(2) Passenger loading area and facilities which principally serve carpools and vanpools.(3) Fringe and transportation corridor parking facilities or portions thereof which are reserved exclusively for use by carpool and vanpool passengers and vehicles.(e) As required by section 163 of the Surface Transportation Assistance Act of 1982, approval of Federal-aid highway funding for a physical construction or resurfacing project having a carpool lane(s) within the project limits may not be granted unless the project allows the use of the carpool lane(s) by motorcycles or it is certified by the State that such use will create a safety hazard. This requirement does not apply to high occupancy vehicle lanes which exclude carpools or to carpool lanes constructed by the State without the use of Federal-aid Highway funds. The issue of the extent of utilization of these facilities including those constructed prior to January 6, 1982 with Federal-aid Highway funds is a matter for individual determination by the State Highway Agency.