http://reply.papertrans.cn/2/200/19974/19974-31.png
http://reply.papertrans.cn/2/200/19974/19974-32.png
http://reply.papertrans.cn/2/200/19974/19974-33.png
Submitted on: 29 August 2013.
Revised on: 10 November 2013.
Accepted on: 20 December 2013.
___________________JOURNAL OF TRANSPORT ECONOMICS AND POLICY
http://reply.papertrans.cn/2/200/19974/19974-35.png
Submitted on: 16 July 2014.
Revised on: 03 September 2014.
Accepted on: 20 October 2014.
___________________JOURNAL OF TRANSPORT ECONOMICS AND POLICY