I saw the document today announcing the improved roundabout capability of the simtraffic model - I'd like to offer a couple suggestions that would further improve Simtraffic's roundabout simulation.

1) Pedestrian crosswalks setback - most pedestrian crosswalks are designed 1-2 car lengths back from the yeild line.
2) alter the lane model. a lot of roundabout's I'm reviewing lately don't have a uniform number of lanes in the circulating roadway. For example, a 4-lane road intersecting a 2-lane road may only have 1 lane in the circulating roadway on 2 legs.
3) include a feature to better define splitter island geometry.
4) lane assignment in the circulating roadway. (might substitute for lane assignment at the approach...)

Eric Royer
Caltrans