The Tyburn Railroad operates some trackage around Dillerville. These two states alone had almost a third of the country's interurban trackage. Between 1840 and 1860 the total length of railroad trackage increased from to . Freight trains operate on parts of the NEC through trackage rights. The DD1 electric locomotives were developed from the prototypes that were tested on LIRR trackage. Much of its historical trackage remains in use by other railroads. The Canadian Pacific Railway operates other trackage in Beloit. Canada has two Class I freight railroads, both of which have trackage in the US. Mexico has two Class I freight railroads, one with trackage in the US. It was the only regularly scheduled steam excursion over mainline trackage in North America. During this time the streetcar companies continued to expand both trackage and service. The coaling tower, most trackage, and structures were removed. It also operates on New Mexico Rail Runner Express trackage. SCL was later absorbed into CSX, which has abandoned redundant trackage. Sizes under rail are usually for lighter duty freight, low use trackage, or light rail.