Round Rock's first DDI gets off to a rocky start

[Marc]

Central Texas' first diverging diamond intersection (DDI) opened Friday morning... three hours behind schedule. Crews had the intersection at RM 1431 and IH 35 shut down Thursday night in preparation for a pre-rush hour 5:00 a.m. unveiling. Well, 5:00 a.m. came and went and crews were still not finished re-striping the road and installing a sign gantry. Rush hour started and traffic started to build on both sides of the interchange. BIG TIME! It took me an hour to drive the three miles from my house to the interstate. The intersection was opened throughout the course of that hour and I will say traffic started to move a lot better once it did.

Interestingly enough, what really frustrated me was the amount of people calling into our talk radio station bashing the new interchange (even the hosts were bashing it). People were quick to blame the new "whacky" interchange for the traffic problems rather than the simple fact it opened way behind schedule.

Needless to say, I'm excited to see how it improves the traffic flow in the area (I'm already noticing an improvement and it's only day three). There are two additional DDIs planned for Austin: IH 35 at Parmer Ln. and Mopac Expy. at Slaughter Ln.

Here's a clip from KXAN news (not a fan of this channel, but they were the only ones that did a story on it):

[Chris]

It appears that they built a bypass for the frontage road alongside I-35. In a regular DDI configuration, the frontage road would become non-continuous, as you can only make a left or right turn, and not cross straight ahead.

Given the fact that most of Texas' freeways have frontage roads, I doubt if DDIs would become a common sight in Texas. One major advantage of a DDI is the low cost, as it can usually utilize the existing overpass. But if you have to construct bypasses for the frontage roads, the cost would increase considerably in most situations.

[dfwmapper]

I expect to see more instances of continuous-flow left turns being built, at least in cases where there's some extra space surrounding the interchange, the freeway passes over the crossroad, and turnarounds are already in place. The first one in Texas was at the I-35/SH 80 interchange in San Marcos.

[yakra]

I expect to see more instances of continuous-flow left turns being built, at least in cases where there's some extra space surrounding the interchange, the freeway passes over the crossroad, and turnarounds are already in place. The first one in Texas was at the I-35/SH 80 interchange in San Marcos.

I don't see anything out of the ordinary here, in either Google, Bing, or OSM... have changes happ[ened that aren't reflected in online maps or aerials yet?

[Chris]

It's somewhat of a CFI. Traffic making a left turn from SH 80 to I-35 cross over to the left side of the road.

[yakra]

Oh, I see it now. Subtle!