High-speed G/D‑series trains on the Shanghai to Mianyang route typically involve one transfer at Xi’an North or Chengdu East. Fuxing G‑series sets (CR400AF/BF) run up to 350 km/h (217 mph) on the Shanghai–Nanjing–Xuzhou–Zhengzhou–Xi’an high-speed corridor, then continue west at 250 km/h (155 mph) on the Xi’an–Chengdu high-speed railway, with the final section toward Mianyang on the Chengdu–Mianyang line at around 200–250 km/h (124–155 mph). These services offer Second, First, and often Business Class, and the fastest end-to-end journeys take about 10–12 hours depending on the connection and intermediate stops. In contrast, conventional Z/T/K overnight trains cover the whole distance on older routes via the Qinling Mountains and the Baoji–Chengdu line, generally operating at 120–160 km/h (75–99 mph) on flatter sections and slower in mountainous segments. They provide Hard/Soft Seat and Hard/Soft Sleeper classes, plus a dining car, with total travel times roughly 28–34 hours. For speed and frequency, choose high-speed G/D services with a transfer; for an overnight budget option, the direct conventional sleepers are available.