5.2. SR 07-24-2000 - Laserfiche WebLink

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lanes and the shoulder widths. The medians place the barrier in the middle of the road. The chokers narrow the curbline and place the barrier at the roadway's edge. Various choker widths have been tried between 20-feet and 28-feet on residential streets. Before a design was approved, temporary curbing was used to test the results. The initial chokers were installed only at intersections, believing that property owners would object to the irregular curbline in front of their homes. Results showed that the 28-foot chokers had no impact on travel speeds. Restrictions down to 20-feet were needed before any appreciable speed reduction was noted. Unfortunately, the narrow chokers caused problems for larger vehicles such as trash trucks and moving vans when located adjacent to a intersection. Chokers at the corners are viewed as pedestrian amenities. They improve visibility for both the drivers and pedestrians and the reduced roadway width minimizes the pedestrian's crossing time. A revised plan relocated the chokers to midblock locations. The restrictions had the desired effect of speed reduction without impacting the turning radius at the street corners. The midblock chokers are only used in new subdivisions, thus minimizing the homeowners concerns with on-street parking. Some special design considerations are needed to ensure compatibility with the surrounding neighborhood. Median islands presented similar impacts and results to those found with the traffic chokers. The roadway width was set at 21-feet adjacent to the islands. This allows for a 12-foot travel lane and on-street parking. Speeds were reduced in most cases. The only problems encountered with left-turn restrictions at residential driveways. Careful planning is needed to retrofit existing subdivisions. For new subdivisions, the islands are planned to be small enough that at least some part of the individual lots has left turn access. The builders can probably figure out how to fit the homes on the lots. Block Lengths The final design strategy was to examine the impact of shorter block lengths within the subdivision. Some developers want a grid street system and some parcel sizes are too restrictive to allow curvilinear roadways. We've explored the use of shorter block lengths, believing that more frequent intersections increase driver expectation and result in lower speeds. Unfortunately, this design change really impacts the development cost and one example was available for review. The developers, of course, wanted longer block lengths. The fewer number of cross streets increases the number of saleable lots and decreases the amount of roadway that has to be constructed. The developers typically build to the greatest block length allowed under the existing subdivision' ordinance. Very little data is available from local traffic counts for the various block lengths. The limited data show minimal speed differences for subdivisions with long and short block lengths. Block length was not viewed as a major determinant of travel speed.