Jerry Ong speaks about flawed Imperial TIA

Dear Editor,

I had been following the apartments proposed for Imperial Development in Sugar Land, specifically Historic District 1 and 2, since its traffic would directly affect my neighborhood.  Being a Civil Engineer, I had thought that any traffic concerns would be absolved by the Traffic Impact Analysis (TIA), a traffic study of the Imperial Development paid for by the Developer (Johnson Development).  Upon obtaining a chance to review it, I found several discrepancies and errors.

I then did what is know in Engineering as a “sanity” check, a review of the final results to see if they made sense.  My conclusion was that the TIA is flawed, at least as far as traffic in the Historic District is concerned.

Some background is in order:

1. First, the old Imperial Sugar plant (aka Historic District 1) is traffic impaired.  It is bounded on the East by Main Street, a purely residential street running North-South through one of Sugar Land’s oldest neighborhoods, known as “The Hill”.   On the South, it is the main exit to Highway 90, restricted by a Union Pacific railroad track.  The only North exit is through Mayfield Park, another older neighborhood of 122 homes just North of the Imperial Sugar plant. Ulrich Street, largely residential through Mayfield Park, runs North-South from Highway 90, tie-ing into Main Street/Burney Road through Harmon Street.

2. By 2019, the Developer plans to add in Phase III to the Historic District:  325 apartments, hotel,  theatre,  museum, water park,  corporate office, extensive retail and restaurant establishments, and at least 3 parking garages in addition to the existing Farmer’s Market, with a new road (already built) from Ulrich going West to the new Ballpark by Highway 6.

3. Union Pacific is already planning to add a second and parallel railroad track, expecting to have 70 trains per day.  In the Stafford/Sugar Land area, the railroad has averaged 4 accidents per year.

Harmon Street, being the only North exit for all these development, was identified as a key point for the “sanity” check.  The TIA gives 2011 recorded traffic levels and predicts 2019 traffic levels (in vehicles/hour).  Numbers directly from the TIA forecasts only a 9% to 11% increase in traffic for both North-bound and South-bound traffic for Harmon Street.  This appears far too low for the planned improvements.

To estimate what the traffic level should be, I choose to compare the same 2011 and 2019 conditions based upon vehicle trips generated from sources in the Historic District, based upon the Institute of Traffic Engineers (ITE) Trip Generation Manual.  These are expected vehicle trips per hour for the PM peak hour produced by a given source.

For 2011, the summarized total trips per PM peak hour are:

Mayfield Park:  122 homes x 1.01 (ITE code 210, Single-Family Detached Home) = 123 trips

Nalco Industries:  500,000 square feet x .00073 (ITE code 140, Manufacturing) = 365 trips

TOTAL for 2011 = 488 trips/hour

For 2019, for the Developer’s new planned improvements:

Apartments: 325 unit x .62 (ITE code 220, Apartment) =  264 trips

Hotel: 250 rooms x .59 (ITE code 310, Hotel) =  148 trips

Retail: 652,000 square feet x .00373 (ITE code 820, Shopping Center) x 50%  = 1216 trips

Office: 1,125,000 square feet x .00149 (ITE code 710, General Office Building) x 20% =  335 trips

TOTAL for 2019 (above % is estimated Phase III portion in the Historic District) = 1962 trips/hour

As the Apartments and Mayfield Park have similar characteristics, a low estimate would be:

(488 + 264 ) / 488 = 1.54  54% increase in traffic

For a high estimate: (488 + 1962) / 488 = 5.02 402% increase in traffic

Both of these are so much above the 11% that I would conclude that the TIA is flawed.  It may predict the Ballpark traffic but not the Historic District traffic.

As reinforcement:

1.     The TIA is only an estimate based upon a mathematical model of the traffic.  As such, it is probably at best +/- 10% accurate.  This means that the increase in traffic could be as high as perhaps 22% or as low as 1%.  The 1% is absurd in that the TIA is predicting virtually no change in traffic levels at Harmon with all the future traffic sources anticipated.  While most of the traffic will go South to Highway 90, the TIA is predicting about 98 to 99% of the new traffic will avoid Harmon.

2.     If 100% of the Phase III retail development is for the Historic District, an upper bound could be up to (488 + 1962 + 1216) / 488 = 7.51, almost eightfold the existing traffic level.

3.     As an additional check, I calculated the TIA predictions for Burney/Main at Harmon.   The results showed a 14% to 35% increase.  This also seems too low for the main East and North bound artery to the area.

4.     It has been argued that traffic will go North by the new Westbound road at Ulrich.  I contend that the only reason a driver would drive halfway to Highway 6 and then double back to the North is that he knows that the traffic is too bad to take Harmon.  This is not consistent with the Level-of-Service (LOS) of “C” predicted by the TIA for the Harmon/Burney intersection.

5.     The TIA reported that the average length of time the railroad arms at Highway 90 were closed was 2 minutes 12 seconds.  For 70 trains, this means that the main Highway 90 access from would be fully blocked 10% of the day.  Along with any train/auto accidents, this would encourage further traffic to go North through Harmon and East through Main.

6.     Moving the apartments, or changing them to fewer townhomes or patio homes would mean up to a 13% reduction in the traffic source.

Along with the Developer, Sugar Land’s Engineering, Planning and Zoning Commission, and the City Council have stated that the traffic can be “mitigated”. How can you know you can mitigate the traffic if you do not know or will not acknowledge what the traffic levels are?  While you may be able to mitigate 50% additional traffic, a five fold increase is another story.  In my opinion, that would take a new road to the North/East and/or an overpass/underpass to the South to eliminate the railroad block.

The City of Sugar Land is proceeding with a PD (Planned Development), the Developer will let contracts for land to be developed, and by the time the true impact of the traffic is known, too much will be built or in place to do anything significant.  The “mitigation” steps will fall mainly on the residents of Mayfield Park and The Hill, who really can do little except to endure the traffic on their streets (or move).  The real tragedy here is the Developer is supposed to accommodate the traffic and the City is responsible to enforce it.  What happened to the “Planning” that was supposed to occur here? –all because of a flawed TIA.

Jerry Ong, PE (Texas and Louisiana)

P.S.  I would welcome the opportunity to meet with the TIA authors and to change my numbers or be proven wrong.

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Posted by on May 2 2012. Filed under Letters. You can follow any responses to this entry through the RSS 2.0. You can skip to the end and leave a response. Pinging is currently not allowed.

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