That cannot be an emperical statement. Traffic engineers have absolutely wrecked the american city, largely be ause they didnt know the impact of adding lanes.
It's not the only reason. I think that traffic engineers lack/lacked a feel, a certain gut understanding , an inability to feel through the skin. Just look around you. See and hear them at municipal meetings. They are unable to sensually experience the effects of their work, their praxis.
I've spoken with traffic engineers before, and the consensus I've gotten is that, excusing a few bad apples, much of the problems originate with popular or political interference.
Who's to say they aren't the same as the developers implementing all the bad stuff at <pick your favorite hated tech company>? Listen to what they say, and plenty know it's bad, but they shrug their shoulders because that's what the bosses want and the pay is good.