Spot Speed Spot Speed is defined as the instantaneous measure of speed at a specific location on a roadway (Sigua, 2008). Spot Speed is done to determine the following: range of allowable speeds as a basis for setting standards, set maximum and minimum speed limits, the need for posting advisory speed signs, for school zone protection, and to assess the performance of a traffic control devices. The survey was done in Magsaysay Street, UP Diliman. A total of 51 vehicles (bicycles included) were accounted. I. . Procedure There are several ways to do Spot Speed, but for this activity, the Manual Method was used. The procedure is as follows: 1. Determine trap length: 30m 2. Determine travel time of vehicles at that trap length using a stop watch. 3. Determine speed. 4. Compute for k. where k = number of class intervals = 1+3.322log(n) (n=number of vehicles observed) 5. Get the mid class (x), frequency (f), % frequency of every speed class. 6. Given these, the mean, variance, standard deviation, median, 15th and 85th percentile can be computed. 7. Graph the Spot Speed Frequency Histogram and Cumulative Frequency Curve. II. Computation From the data gathered found in the appendix, table 1 is computed. = 1+ 3.322 log(51) = 6.6725 7 interval per speed class = ( )/ = (55.95 -16.16) / 7 = 5.684 6 III. Results and Discussion Table 1. Summary of Data Speed Class Mid class, x Frequency, f % Frequency Cumuative Frequency !

16-21.99 19 6 12% 12% 114 2166 22-27.99 25 16 31% 43% 400 10000 28-33.99 31 14 27% 71% 434 13454 34-39.99 37 11 22% 92% 407 15059 40-45.99 43 2 4% 96% 86 3698 46-51.99 49 1 2% 98% 49 2401 52-57.99 55 1 2% 100% 55 3025

Table 2. Results mean speed 30.35600303 variance 65.59497409

SD 8.099072422 median 30.25210084 mode 25

15th percentile 22.54707113 85th percentile 38.57192056

Figure 1. Spot Speed Frequency Histogram

Figure 2. Cumulative Frequency Curve Given the values from tables and 1 and 2, the Spot Speed Frequency Histogram and Cumulative Frequency Curve is plotted. The 85th percentile

0 5 10 15 20

16-21.99 22-27.99 28-33.99 34-39.99 40-45.99 46-51.99 52-57.99

Freq

uency, f

Speed, kph

Spot Speed Frequency Histogram

0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

0 10 20 30 40 50 60

PERC

ENT VE

HICLE

S AT

OR BE

LOW

SPEE

D SHOWN

Speed, kph

Cumulative Frequency Curve

represents the critical speed. This is the maximum speed limit- meaning speeds exceeding the 85th percentile are considered to be driving faster than safe conditions. The speed corresponding to the 15th percentile is the minimum speed. Driving below this speed may cause flow obstruction, traffic, and increase accident hazard. Of the 51 vehicles surveyed, 4 exceeded the maximum speed limit while 6 went below the minimum speed limit. Determining the 85th percentile gives the road engineers an idea of what speed limit must be set on that road considering the surroundings and road properties. IV. References Sigua, R.,(2008). Fundamentals of Traffic Engineering. The University of the Philippines Press. Quezon City, Philippines Appendix count type Time, s Speed, kph 1 bicycle 6.68 16.16766467 16 motorcycle 6.10 17.70491803 49 car 6.09 17.73399015 35 delivery truck 5.55 19.45945946 39 car 5.48 19.7080292 15 motorcycle 5.05 21.38613861 33 car 4.86 22.22222222 9 car 4.80 22.5 2 car 4.78 22.59414226 38 motorcycle 4.74 22.78481013 50 car 4.68 23.07692308 13 car 4.58 23.58078603 6 car 4.58 23.58078603 32 car 4.48 24.10714286 20 car 4.41 24.48979592 25 car 4.41 24.48979592 45 car 4.30 25.11627907 18 car 4.00 27 44 truck 3.96 27.27272727 31 car 3.91 27.62148338 5 car 3.90 27.69230769 26 delivery truck 3.88 27.83505155 34 car 3.66 29.50819672 19 car 3.65 29.5890411 4 car 3.65 29.5890411 48 motorcycle 3.57 30.25210084 24 car 3.56 30.33707865

51 car 3.56 30.33707865 3 motorcycle 3.55 30.42253521 21 car 3.54 30.50847458 12 car 3.31 32.62839879 10 car 3.30 32.72727273 22 car 3.28 32.92682927 41 motorcycle 3.28 32.92682927 14 car 3.20 33.75 8 motorcycle 3.20 33.75 43 car 3.11 34.7266881 27 car 3.06 35.29411765 36 car 3.06 35.29411765 46 car 2.97 36.36363636 37 car 2.89 37.37024221 47 car 2.84 38.02816901 40 motorcycle 2.81 38.4341637 30 car 2.79 38.70967742 17 car 2.75 39.27272727 42 car 2.73 39.56043956 28 delivery truck 2.72 39.70588235 23 car 2.59 41.6988417 7 car 2.50 43.2 29 car 2.29 47.16157205 11 motorcycle 1.93 55.95854922