Res 1989-134 - Laserfiche WebLink

Home Browse Search

Accompanying the travel time run will be a description of the street geometry for each section of the street. A section is defined as the portion of the street extending from the stop line of one controlled intersection to the stop line of the next controlled inter- section downstream. Section length, number of lanes, and posted speed limit should be recorded. If the posted speed changes in the section, a weighted average should be calculated based on distance. For example, a section of street is 800 feet lon~, and is posted for 30 mph in the direction under consideration for 500 feet and 40 mph or 300 feet. The average posted speed 'auld be (30 mph x 500 feet~õÎë~40 mph x 300 feetl 800 eet = 33.75 mph Number of lanes is measured at the stop line at the beginning of the section, not including turn bays. For each street, average daily traffic counts should be provided. Data up to five years old is acceptable as long as significant changes in traffic patterns have not occurred. Free flow travel time should be calculated assuming no stops and traffic flow at the average posted speed limit. The free flow travel time for each section is the section length divided by the speed in feet/sec. Speed in mph is converted to feet/see by multiplying by 1.47. The total free flow travel time is the total of the section free flow travel times. The delah is the difference between free flow travel time and actual travel time, averaged from t e travel time runs. For example, a street contains two sections. Section 1 is 800 feet and has a 35 mph average posted speed limit, and Section 2 is 1200 feet long and has a 40 mph average posted speed limit. The free flow travel time would be 800 feet 1200 feet 35 mph x 1.47 + 40 mph x 1.47 = 36 seconds The Qualit¡' of Service Summary form has been provided to allow the convenient orga- '1ization 0 this data. One form should be filled out for each combination of street and tirection. Applicants should duplicate the form as necessary. àummarv The procedure outlined here will provide a rough synopsis of the existing typical worst case situation using data that can be collected very quickly. For arterial systems, only data alonÏ:, the arterial is necessary. The runs have been defined to eliminate the in- clusion of oundary conditions (such as side street delay on an arterial), which, though they may inhibit a complete understanding of the situation, will allow arterial and grid networks to be compared in a similar light.