Question

(10 pts) According to counts taken 3 years ago that are available on the ADOT’s website, SR441 had an AADT value of 17,140 in downtown Tucson. While waiting for PAG or ADOT to retrieve the hourly traffic counts for SR441 from its archives, the city engineers decided to use the Florida default values to begin his analysis. A short time later, the requested data - the peak hourly volume was 1779. (a) What K-factor should the city engineer have used in his preliminary analysis while waiting for hte state’s data? What is the resulting peak volume? (b) What K-factor did thesegment of SR441 acctually have, according to the state’s data? (c) What is the impact of using the Florida data? Typical K-Factor for Florida Roads Typical K-Factors for Florida Roads Area Types K-Factor Urban 0.093 Transitioning/Urban 0.093 Rural Developed 0.095 Rural Undeveloped 0.100

Answer 1

If I'm not wrong, ADOT stands for Arizona Department of Transportation and the state of Arizona does have a city named Tucson. But the State Route 441 belongs to Florida. So, why would ADOT have SR 441's data? That too, in downtown Tucson?
Anyway, coming back to the problem
(a) K-factor is defined as the proportion of AADT occuring in an hour. Four different typical K-Factors for different area types for the State of Florida is given in the question.
Now, since Tucson is an urban area, the city engineer must have used 0.093 as the K-factor as per the given data.
The resulting peak hourly volume, therefore, will be given by
Peak hourly volume = K-Factor x AADT = 0.093 x 17140 = 1594.02 or 1595

(b) The actual K-Factor according to the state's data will be
K-Factor = Peak hourly volume/ AADT = 1779/17140 = 0.104

(c) As we can see from the results, the actual peak hourly volume is much more than the roughly estimated peak hourly volume using the typical Florida K-Factor values. This difference can cause major problems in planning and design of future expansion or widening projects if not taken care of properly. The resulting road projects will be inefficient to handle the peak hourly traffic since the design values were taken less than the actual values. More over, a healthy volume to capacity ratio will not be maintained and the roads will be prone to accidents.