Everyone knows about traffic congestion in Boston. It’s why we’re often late for meetings. It’s why sightseeing firms are paring back their tours because the tourists are spending too much time sitting in traffic. And it’s why many Boston officials are worried Amazon will take a pass on the city -- traffic is just too heavy already.

What a lot of people don’t realize is that the federal government is subsidizing this congestion. Tax policies approved in the 1970s and 1980s give a break to people who drive to work and park in employer-provided or employed-subsidized parking spots. Normally that type of fringe benefit would be taxed as income, but under federal law employees are granted an exemption of up to $255 a month.

The federal tax break is most valuable to people in the highest tax brackets who are commuting to areas where parking is most expensive. “We’re subsidizing them to drive in precisely the places and at precisely the times that experience the most congestion,” said Tony Dutzik, a senior policy analyst at the Frontier Group, during a Codcast interview with Josh Fairchild and James Aloisi of TransitMatters.