[7] Walder was born in Indianapolis and grew up in the Rockaways in the New York City borough of Queens, where he attended Beach Channel High School.

His appointment came with Motivate's announcement of the Bikeshare Holdings acquisition, promising new leadership, $30 million infusion of cash, relocation of headquarters from Portland to NY, and immediate expansion for Citi Bike.

[18] Walder is a member of MIT's visiting committee for the Department of Civil and Environmental Engineering[19] and Harvard Kennedy School's Board of Advisors of the Taubman Center.

[20] In 2013, Walder gave the Gustav Pollak lecture in the John F. Kennedy Jr. Forum at Harvard, titled "From Queens to Hong Kong: More than Just a Train Ride".

[25] In April 2014, at the Hong Kong transit company MTR Corporation, local newspapers revealed a two-year delay to the high-speed cross-border rail link.

[27][28] Walder had been facing calls to quit after a report submitted to the legislative council said he had stopped the secretary for transport and housing from telling lawmakers about the delay.