This should do it:
routes.MapRoute(
name: "About",
url: "About",
defaults: new { controller = "Public", action = "About" }
);
routes.MapRoute(
name: "MyPageSummary",
url: "MyPage",
defaults: new { controller = "MyPage", action = "Summary" }
);
routes.MapRoute(
name: "Default",
url: "{controller}/{action}/{id}",
defaults: new { controller = "Public", action = "Start", id = UrlParameter.Optional }
);