Detailed Instructions: In this task, you're given a passage, further information available on a particular linked term from the statement, and an answer term. Your job is to generate a question that can use the information provided to obtain the given answer. You should use the information on both passage and link information to create the question. Note that the answer to the question should be exactly the given answer, and if the answer is none, the answer to the question shouldn't be obtainable from the passage or linked information.
Problem:Passage: After leaving Union Station and crossing the Los Angeles River, the line follows the San Bernardino Freeway and El Monte Busway until just after the Cal State L.A. station; it then runs in the median of the San Bernardino Freeway to the El Monte Station along the former route of the Pacific Electric Railway's San Bernardino Line. Starting at El Monte, the line parallels the Union Pacific's Sunset Route (ex-Southern Pacific) for a few miles before turning northeast at Bassett onto a Southern Pacific branch. At (a former Southern Pacific/Pacific Electric-Santa Fe crossing), it switches to the Santa Fe; from Claremont to just west of San Bernardino it follows what was the Santa Fe's Pasadena Subdivision (and before that the Second District of the LA Division, the Santa Fe passenger main line). The San Bernardino Line is mostly single track with 6 passing sidings and short sections of double track near Covina, between Pomona and Montclair, and west of Fontana.
Link Information: none Answer: none
Solution:
In what year did construction begin on the roadway that the San Bernadino Line follows after crossing the Los Angeles River?