Legacy Parkway in Davis County is a different sort of freeway. It bans trucks. The speed limit is just 55 mph. Its mere two lanes in each direction have rubberized pavement to dampen sound — all designed to help adjacent wetlands and wildlife. But that could change dramatically in a little more than a year, on Jan. 1, 2020. That is when a 15-year deal expires, initially drawn up to end lawsuits by environmental groups against the highway. The truck ban will disappear that day, and the state is then free to raise the speed limit or look at widening...