Study on target value of speed for Xi´an metro line 3

Xi´an metro line 3 is an over length route which tends from north east towards south west for 50.5km in total, so it is necessary to study the speed goals of the line. Based on the analysis of the goals of operating time, three top running speeds (80 km/h, 100km/h, 120km/h) were taken in alternative schemes to discuss the influence of various factors in terms of technology and economic. Through study on the characteristic of passengers flow, transport time, running technology targets, adjustability between stations, metro vehicle´s quantity and expense, and effects on system of traction power supply etc, the paper conclude that 80km/h is the most advantageous top running speed for Xi´an metro line 3 in view of energy-saving, environmental and economical aspects, which also keep in order with national energy and sustainable development strategy.