Nobody seems to know yet why two Indego riders ended up on I-676, but one point of interest that arose out of the discussion on Twitter was the apparent ease of accidentally getting onto 676 on your bike.
These two aren't the first to have done it, admitted a few of our Twitter correspondents who had also made this chilling error.
Philip Pierdomenico pointed out that the cyclists must have gotten on at 8th Street, because they were east of Broad travelling west, and that's where you'd have to enter to mistakenly get on 676 at-grade.
Here's what the entrance looks like over there. There's a sign for local traffic to 8th Street and Chinatown on the left, but the middle lane takes you onto 676. Get on the wrong one, and you're in for some trouble:
Why anyone would want to bike on major auto routes like the ones around the 8th Street ramp in the first place, even if they weren't meaning to get on 676, is left as an exercise for the reader, but it seems more plausible that inexperience and confusion are the culprit here, rather than purposeful joy-riding.
Nobody we talked to had ever gotten on at 8th Street by mistake, but interestingly, a few people had accidentally gotten on the 676 entrance at 24th and the Parkway, which turns out to be very easy to mistake for a local street.
Heading southeast on the Parkway near Eakin's Oval, the 676 entrance is only marked as 24th St. There is no signage near the turn informing you that you're about to get on 676: