The percentages of trips with these five travel modes were 21.1%,
14.6%, 13.3%, 24.7% and 26.3% in this GPS survey, while that of a
Shanghai household travel survey (SHTS) in 2009 were 26.2%,
13.5%, 15.2%, 25.1% and 20.0%, respectively (Lu & Gu, 2011) (The
2014 SHTS report has not been published yet, so the 2009 SHTS
data is the most recent data available)