Loop 1604 “super-street” previewed

Late last month, the Alamo Regional Mobility Authority held a public meeting to show plans for a super-street and other related improvements on Loop 1604 West.  (My vacation started immediately after the meeting, thus the reason I’m just now getting around to writing this.)  At this time, the plans include super-street intersections at New Guilbeau and at Shaenfield and ancillary improvements at Braun and at SH 151 (with work on the former now underway.)  Here are the details of those planned improvements.

First, the super-street intersections.  At New Guilbeau, since it’s a T-intersection, it will get half of a standard super-street intersection.  That is, all traffic coming from New Guilbeau will turn right onto northbound 1604.  Traffic then wanting to head south will take a turnaround located across from the Sonic at Amelia Pass.  Southbound Loop 1604 traffic will still be able to turn left onto New Guilbeau.  Northbound 1604 traffic (e.g. traffic coming from Bowen’s Crossing) wanting to make a U-turn at New Guilbeau will instead proceed to the aforementioned turnaround at Amelia Pass.

At Shaenfield, the city of San Antonio is currently looking for expedited funding to extend Shaenfield from Loop 1604 east to Weybridge St. near Burke Elementary School.  This would improve access to and from Northwest Crossing and take some traffic off of Bowens Crossing and Culebra.  With that in mind, the intersection at Loop 1604 and Shaenfield is currently planned to be a standard four-way super-street intersection.  Traffic from both directions on Loop 1604 would be able to turn left onto both the existing stretch of Shaenfield as well as the new extension.  Traffic on Shaenfield would be forced to make a right hand turn onto Loop 1604.  Those folks wanting to go the opposite direction on Loop 1604 would then take a turnaround about 1,200 feet (1/4th of a mile) downstream.  Traffic wanting to go straight through on Shaenfield (i.e. from the existing section to the new extension or vice-versa) would also take the turnaround, then make a right turn to get back onto Shaenfield.

As with the US 281 super-street, signals will stop traffic on 1604 allowing vehicles from the intersecting road onto the loop and also allowing vehicles from the turnarounds to enter.  Although this does add additional signals, those signals will have fewer phases than those currently in place, which means they can stay green for Loop 1604 longer.  And actually, the existing southbound through signal on 1604 at New Guilbeau will be eliminated altogether (or set to always be green) since there will be no conflicting traffic there anymore.

Now on to the additional, non-super-street improvements.  At Braun Rd., TxDOT is already working on re-striping Loop 1604 to three lanes in each direction.  This will require a smidgen of additional pavement to be added and some tweaking of the traffic islands.  Adding the extra lane will increase throughput on 1604 during each signal cycle by about 50%, which should reduce delays.  TxDOT is also looking at some additional minor improvements on Braun itself to improve traffic flow, although the options there are limited.  TxDOT is doing this work themselves using discretionary funds.

At SH 151, there’s a two-pronged plan.  Eventually, TxDOT is planning to build an underpass connecting SH 151 to Alamo Ranch Pkwy.  Funding for that is being sought and will hopefully be secured in time to start construction in early 2012.  In the meantime, to improve traffic at that intersection and to provide a detour route for Loop 1604 when the underpass construction begins, the southbound Loop 1604 access road between Culebra and Alamo Ranch Pkwy. will be improved and extended to meet Loop 1604 at a right-angle at SH 151.  The existing entrance ramp onto southbound 1604 in front of the Olive Garden will be removed and replaced with an exit ramp from 1604.  Traffic wanting to access SH 151 will use this exit ramp, follow the access road past Alamo Ranch Pkwy., and then cross 1604 at a signalized intersection and head straight onto SH 151.  This will also allow traffic from Alamo Ranch Pkwy. to access SH 151.  Additionally, an entrance ramp (essentially an elongated right-turn lane) at the 1604/151 intersection will allow traffic to enter southbound 1604 directly.

I admit I was skeptical about this improvement at first since it adds an extra signal to southbound Loop 1604 without any compensating signal cycle reductions.  However, models show an almost unbelievable 85% reduction in morning peak period delays by making this improvement.  When I thought more about it, I understood why.  A lot of traffic turning onto 151 comes from Culebra.  Therefore, all that traffic has to cross the southbound Loop 1604 through lanes.  This causes an enormous amount of disruption to traffic, which creates significant congestion (not to mention major safety hazards.)  Also, traffic in those left turn lanes frequently overflows onto the through lanes.  By keeping all that traffic separated, it will improve overall traffic flow and safety, even if southbound traffic has to stop occasionally for the new signal.

So how much benefit will these improvements bring?  Here are the estimates based on traffic modeling:

The cost for all of this work (except for the SH 151 underpass) is estimated to be about $7.7 million.  Funding has already been secured from several sources including federal stimulus funds, local MPO metro mobility funds, Advanced Transportation District funds from VIA, and TxDOT in-kind expenditures.  If the environmental clearances are obtained this summer as anticipated, work on the super-street intersections and first phase of the SH 151 improvements will likely begin early next year and take about seven months to complete.

For more information (including schematics), see the sites below.

Related links:

• TexasHighwayMan.com – Loop 1604 West Super-Street
• Alamo Regional Mobility Authority – Loop 1604 Superstreet