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Highway 17: Engineer proposes changes to median plan
By Jason Lesley
A traffic engineer’s review of the Highway 17 median plan for the Citizens Coalition for Ocean Highway does not criticize how it was conducted but focuses on areas for further analysis and suggests alternatives.
A report from Eric Tripi, a traffic engineer with Iteris, a national traffic management firm in Charleston, says the state Department of Transportation study supporting a median done by Stantec was conducted appropriately. Tripi recommends looking again at three issues: crash data, signal warrant analysis and alternatives to a raised median.
Tripi says the opportunity to improve safety was one motive behind the median design, but it’s not entirely clear that a crash problem actually exists in the study corridor and questions blaming the configuration of Highway 17 and the side streets and driveways in the 1.9 miles between Baskervill Drive and Waverly Road. Data presented in the concept report showed that 95 crashes occurred in the study area between Jan. 1, 2008, and Dec. 31, 2010.
“It is our understanding that the crash data used in the analysis was compiled from crash summaries and not the actual police reports,” Tripi says. “Police reports can provide greater detail about traffic crashes, especially when trying to determine the cause of a crash. Therefore, the crash data used in the report may not be telling the whole story.”
He adds that DOT reported 203 collisions in the study corridor between Jan. 1, 2007, and Dec. 31, 2011. That number is twice the statewide average for comparable roads, yet no detailed information about the crashes or any definition of a comparable road was provided.
DOT’s study determined that two additional traffic signals would be needed in the corridor to create gaps in traffic to facilitate U-turns. Locations for the signals were based on the two sidestreet-driveways with highest traffic volumes: Hotel-Jetty Drive and the post office/Lachicotte Drive. Based on the signal warrant analyses, these two intersections were found to meet the volume recommended for signalization. “Our concerns in this section center around these signal recommendations,” Tripi’s report says.
The Hotel-Jetty Drive intersection did not meet any volume standards until all left turns from Cannan Shore Road were redistributed to Jetty and all left turns from Tiller, Cannan Shore and Duncan were added to Hotel Drive. No allowance was made, the report says, for drivers on these streets who may decide to make a U-turn instead of going to the signal. This would reduce the number of left turns at the signal.
In addition, Tripi says it’s common practice to discount right turning traffic as it does not benefit from a signal as much as left turning traffic. The DOT study considered both left- and right-turning traffic in its signal analysis. “If all or a portion of the right turns were removed from the analysis, the standards would be more difficult to meet,” Tripi says.
The intersection at the post office met minimum traffic standards, but with 80 percent of existing post office traffic turning right, it appears that a traffic signal would not be warranted.
“Placing a signal at the post office does not seem to make sense, especially considering the uncertain future and general decline of post offices, the minor nature of Lachicotte Drive and the fact it provides no benefit to the street system on the west side of U.S. 17,” the report says.
Tripi concludes that the justification for the signals is to provide gaps in traffic for U-turns. However, there appears to be value in looking at other locations for traffic signals that may better serve the adjacent land users and still aid U-turns. He says signals at Tiller Drive and Parkersville Road would make more sense.
Tripi suggests three alternatives:
No median and organize driveways: It is recommended in this alternative to look for opportunities to consolidate and better delineate driveways. This access management strategy will help reduce the number of driveways in the corridor and make it clearer where drivers need to enter and exit businesses. This will provide a safer environment for the motorist and will add some aesthetics to the corridor. Opportunities for beautification will also be sought in this scenario.
Modify the existing median plan: There appears to be opportunities to alter the existing plan to better suit residents and business owners while still keeping the median plan mostly intact. Recommendations include eliminating signals at the post office and Hotel-Jetty Drive while restricting turns and placing one signal at Tiller Drive, allowing left turns into the south Fresh Market drive and allowing full access at Parkersville and Archer roads. Another potential modification would be to put a signal at Professional Lane after an analysis to determine how it would fit into the corridor and interact with the signal at Waverly. A full traffic analysis would be needed to determine how any modifications would work.
Strategic placement of islands in the center turn lane: In this scenario, full access would be allowed at most intersections with islands being used to better organize the left turns in the corridor. Medians would be placed in locations on Highway 17 where there are fewer driveways.
The islands would prevent drivers from using the center turn lane as another through lane, eliminating confusion and the potential for head-on crashes. The size of the islands would meet state DOT guidelines. Opportunities for beautification would be embraced for the island and median designs.