In a few weeks, the Suffolk County Department of Public Works will institute changes in traffic patterns on County Road 39 between North Sea Road and Magee Street in Southampton to test a pared-down version of an experiment run by the county and Southampton Town last spring. Local officials said the plan, as envisioned by Charles McArdle, Southampton Town superintendent of highways, brought marked improvement in travel times for afternoon commuters and eased bypass traffic on residential back roads. This week, the editors are joined by senior reporter Michael Wright and McArdle to talk about how the new plan will work and some of the Southampton road challenges that remain.