The issue isn't people going too fast, it's people turning left. 26 basically connects Portland on one end and Mt Hood recreation stuff on the other, and it used to be that there wasn't that much in between. Over the last few decades, a lot of development has gone up, meaning a lot more businesses and neighborhoods along both sides of 26, plus the highway has gotten a lot busier.
Every study on this topic says yes. Drivers go faster on roads where they can go faster, regardless of the speed limit. If you set a low speed limit on a road capable of supporting fast cars, people just ignore it - they obviously set the limit wrong, right? But if you make a road where people can't drive fast, they don't and they don't even feel that bad about it.