First RTD contractors will dig two feet under five of the busiest intersections in downtown Denver as transit officials begin a $152 million rail maintenance catch-up blitz to lay new tracks that should be good for three decades. Then RTD crews will paint portions of those intersections red, or another color to be determined in an upcoming “design exercise” – a brighter look intended to improve safety for vehicles and pedestrians. Traffic disruptions and detours will start this weekend and continue through summer. RTD officials are suspending rail service across central downtown Denver but contractors will be “trying to minimize the impact to our customers,” RTD’s general manager Debra Johnson said.