===Track upgrades (overtakes, crossovers, and traffic control)===
[[File:Sunnyvale four tracks (33608468046).jpg|thumb|right|250px|South overtake quad-track section south of [[Sunnyvale (Caltrain station)|Sunnyvale]]]]
CTX added quad-track overtake sections near the cities of Brisbane, Redwood City and Sunnyvale.<ref name=SFC-040601 /><ref name=SFC-040403 /><ref name=BRA-0412>{{cite news |url=http://www.bayrailalliance.org/newsletter/2004/2004-3dec_sot.pdf |title=Caltrain CTX and Baby Bullets boos Ridership 17% |author=<!--Staff writer(s); no by-line.--> |date=December 2004 |newspaper=Staying on Track |publisher=BayRail Alliance |accessdate=26 March 2017}}</ref> During the initial design phase, anovertakes overtake waswere also plannedannounced for Millbrae and Redwood City.<ref name=SFC-011119>{{cite news |url=http://www.sfgate.com/bayarea/article/Fast-train-to-San-Jose-may-boost-L-A-bullet-2853206.php |title=Fast train to San Jose may boost L.A. bullet / Caltrain commuter seen as a first step |author=Gathright, Alan |date=19 November 2001 |newspaper=San Francisco Chronicle |accessdate=25 March 2017}}</ref> Millbrae gained a third track, and Redwood City added two sidings near Redwood Junction, approximately {{convert|1.2|mi}} between Chestnut Street and Fifth Avenue.<ref name=FactSheet /> From north to south, the completed quad-track overtake sections are:<ref name=FactSheet />
# '''Brisbane''', approximately {{convert|2|mi}} between Candlestick Cove and Tunnel #4 (overlaps Bayshore Station)
# '''Redwood Junction''', approximately {{convert|1.2|mi}} between Chestnut Street and Fifth Avenue
# '''Sunnyvale''', approximately {{convert|2|mi}} between Fair Oaks and Bowers (overlaps Lawrence Station)
