If the entrance to Aspen becomes four lanes, the additional flow of traffic down Main Street will make all intersections problematic during the busy times of the day. Traffic lights may be added to allow crossing and entering of Main Street. The time to travel the length of Main Street may actually increase due to waiting at lights. More cars will be looking for parking spaces at the same time. The incentive to use mass transit will be reduced.
The problem is too much traffic, not inadequate roads. To manage the traffic, the first step should be to analyze the kinds of vehicles by purpose. Then, incentives and disincentives can be designed and implemented.
The actual problem is the overdevelopment of the community, and some dubious decisions on creating traffic generators to the west. The hospital was in town. The elementary schools were in town. More affordable housing was built, and more is considered, outside of town. More buildings, east of the bridge, means more maintenance, more service vehicles. More working people are needed to staff more businesses. Expansion of the airport will increase vehicle traffic.
Within a couple of decades it is likely climate change will have serious curtailing effects on the whole Roaring Fork Valley. Continuing to grow Aspen, and the population of the valley, will mean a much more difficult future. While the leadership makes some sympathetic comments about the situation, nothing concrete is being done. Certainly nothing on the scale of what is needed. Business as usual is a hard thing to overcome.