Complex sentence: As street traffic increased in downtown Los Angeles, the Pacific Electric Railway undertook its most ambitious project, a dedicated right of way into downtown through a subway-the existing terminal in the Pacific Electric Building at Sixth and Main was reached by shared street running.
Split into simpler sentences: As street traffic increased in Downtown Los Angeles, the Pacific Electric Railway undertook its most ambitious project, a dedicated right of way into downtown by use of a subway. The existing downtown terminal in the Pacific Electric Building at Sixth and Main was reached by shared street running.