PHF) compares the traffic volume during the busiest 15 minutes of the peak hour with the total volume during the peak hour. It INDICATES how consistent traffic volume is during the peak hour.\({\rm{PHF}} = \frac{{\LEFT( {{\rm{total\;hourly\;volume}}} \right){\rm{\;}}}}{{\left( {{\rm{peak\;}}15{\rm{\;minute\;volume\;within\;the\;hour\;X\;}}4} \right)}}\)Range of PHF\(\frac{x}{{60}} \le PH{F_x} \le 1\)For x = 15 minutes\(\frac{{15}}{{60}} \le PHF \le 1\) 0.25 ≤ PHF ≤ 1∴ The theoretically possible range of PHF for 15-minute sub-hours will be 0.25 ≤ PHF ≤ 1 .