New Zealander Sarah Walker justified her reputation as one of the world's best BMX riders, recording the second-fastest time of the 16 competitors in the Olympic seedings round on Wednesday.
Walker finished in 38.644s, behind Australian Caroline Buchanan, who was timed at 38.434 at the London Games.
The seedings round determines the selection order for the semifinals and final on Thursday.
Walker, 24, finished fourth in the event at the 2008 Beijing Olympics and is a former world champion.
In the men's BMX seedings, Marc Willers was 10th of the 32 starters with a time of 38.687s.
Fellow New Zealander Kurt Pickard was 16th in 39.057s.
Another round will be held on Thursday to reduce their field to 16 for the semifinals and final.