August 11


Here is the story of a common sense approach to gaining approvals for an access that doesn't meet the letter of the law (the county's access spacing guidelines).

I have been working on a project for about a year that just received its final government approvals.  It is a 150 acre development that will have up to 1.9 million square feet of office space, 100,000 square feet of commercial/retail space, and 1,100 apartment/condo units.  The site straddles a north/south county road and is adjacent to the south side of a freeway.  This is a developing area of a second ring suburb that does not have heavy traffic yet, even though the freeway/county road system has been built for significant traffic growth.

The developer believes an access point on the county road approximately 550 feet south of the freeway interchange is integral to getting the development started.  This does not meet the county's access spacing guidelines and I raised this flag at the beginning of the project.  We met with county engineering staff (facilitated by the city's engineering staff) and the county staff said they would consider the access if we could prove it would work with simulations in the year 2030 with full build-out.  We went through an extensive forecasting and SimTraffic simulation effort and to everyone's surprise we came up with a road design where this sub-standard, major access could function without traffic backing up between the closely spaced intersections.  After months of effort, county staff then raised objections because the models don't account for the safety impacts of weaving traffic between closely spaced intersections.

After several more months of discussions between the developer, city, and county (both at a political and staff level), we came to an agreement to allow an interim full movement access.  The developer can build the first phase of the development (about 500,000 square feet of office space and the 100,000 square foot commercial/retail center) with a full median opening.  With each subsequent phase the developer needs to do a follow-up analysis based on the traffic conditions at that time to determine if the full access can remain open.  If level of service or safety problems arise or are forecast for a next phase, the access will be converted to a 3/4 access (lefts and through from the side street will be blocked but lefts off of the main street will remain open) at the developer's expense.  Then if conditions degrade after that, the intersection will be converted to a right-in/right-out which is allowed under the County's access spacing guidelines.  At no time will a traffic signal be installed.

An ultimate roadway and traffic control plan was developed for the area assuming the access will one day be a right-in/right-out.  The appropriate right-of-way is being preserved for this design and the interim roadways are being designed to dovetail into the ultimate design.  I believe the intersection will operate well in the near future because the county road has light traffic volumes for a four lane divided roadway.  As traffic grows, the intersection will be converted to provide the appropriate level of access.  This is a great compromise solution that will allow the developer to gain momentum with the development while at the same time protecting the city and county's transportation system.

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Mike Spack

My mission is to help traffic engineers, transportation planners, and other transportation professionals improve our world.

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