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Friday, June 19, 2009

Click here to enlarge this photo Staff photo by EMILY BARNES A Maryland Independent reader wants to know why the speed limit is 45 mph on the new St. Charles Parkway extension. E-Mail This Article | Print This Story

I am very happy with the new St. Charles Parkway-Rosewick Road between Waldorf and La Plata. It's four-lane and limited access, a very convenient alternative to U.S. 301.

My question is why the speed limit is only 45 mph? It doesn't seem to be consistent with other roads in the area, such as Route 488, which is much more congested, higher speed limit and only two lanes. It seems that the new road is very heavily patrolled by police and there are selective enforcement points set up at least two or three times a week. To the average citizen, this lower speed limit seems to have more to do with collecting revenue than public safety. Can you shed some light, please?

Mike Mannchen, Waldorf

Michael K. Hinchy, the county chief of development services, sent along a version of this response prepared by Donna Daugherty, highway engineer, and Tony Puleo, transportation planner.

"In response to the inquiry, please note that Charles County seriously takes into consideration the health, safety and welfare of the general public and motorists traveling on our public roadways. St. Charles Parkway and Rosewick Road are designated as minor arterial roads in the Charles County comprehensive plan. Therefore, these roads were designed to minor arterial parkway standards according to the county road ordinance, with a design speed of 50 mph. In accordance with the standards of the American Association of State Highway and Transportation Officials' "A Policy on Geometric Design of Highways and Streets," the design speed for a roadway is used to govern road geometry such as minimum horizontal curve radius, vertical curves, superelevation, intersection spacing, sight distance etc. This document provides guidelines for road design as practiced throughout Maryland and the United States.

"The posted speed limit is typically 5 to 15 mph below the design speed for safety. The new portion of St. Charles Parkway south of Billingsley Road as well as Rosewick Road are posted with a speed limit of 45 mph. In order to increase the posted speed limit, the roadway has to be designed at a higher design speed. The issue of posted speed was raised in the past and at that time, the design engineer reviewed the plans and determined that the design speed could not be raised higher than 50 mph. Therefore, it was determined that the posted speed limit of 45 mph would remain.

"Even though the existing limited development makes these roads feel like rural expressways, the comprehensive plan shows that these roadways will be at the center of future residential, employment, industrial park and mixed use districts extending from La Plata to Waldorf. Considering future development and traffic generation, a 50 mph design speed and 45 mph posted speed limit is not unreasonably low.

"Finally, the question stated that the speed limit on the two road extensions is not consistent with other roads such as [Route] 488. Route 488 is a state roadway which has been in existence for a long time, constructed under previous highway design standards, carrying more traffic each year. In the design of St. Charles Parkway and Rosewick Road, Charles County has anticipated growth in traffic and followed currently accepted engineering standards provided by AASHTO as well as the road ordinance, "Standard Specifications for Construction," and the "Standard Details Manual." Therefore, a direct comparison to Route 488 is not equal. Compared with other county minor arterial parkways, such as Middletown Road, St. Patrick's Drive and Smallwood Drive, the posted speed limit on the two new parkway extensions is appropriate.

"Given this explanation of the planning and design process of these road projects, please understand that increasing county revenue through artificially reducing speed limits plays no factor in setting the speed limits on new Charles County roadways."

Got a question that's been bugging you? Ask me anything attempts to answer queries on a variety of topics from Maryland Independent readers. Send your questions to Joel Davis at jdavis@somdnews.com or 7 Industrial Park Drive, Waldorf, MD 20602. Include your name, hometown and a phone number for identification purposes.