Traffic Operations Flashcards
Define the sample mean
Average; x=sum(xi)/n; where xi is the observations and n is the number of observations
Define the median
The 50th percentile value, half the sample observations are less than the median
Define the mode
The most frequently observed value
Define Central Tendency
mean, median, mode
Define DHV
Design hourly volume
Define a volume adjustment factor
Ex. F=ADT/Tuesday ADT provided adjustment factor
What are the uses of spot speed studies
speed trends over time, establish speed limits, traffic sign placement, no passing zones, intersection sight distance, before after studies, crash analysis
Discuss important factors in selecting spot speed studies
Consistent with study purpose, not where vehicles are accelerating or decelerating, data collectors cannot influence speed, or enforcement actions
Define sample size calculation
N=((Sx(K/E))^2; where N is min sample size, S in the sample sandard deviation, K is the statistical constrant (1.96 for 95%, 2.58 for 99%) and E is permitted error in average speed estimate, typically 1mph
What are some of the important factors in speed zoning
speed limits should be within 5mph of 85th, other characteristics include Pace, Roadside development, parking, road geometry, crash experience
What is the purpose of travel time studies
Congestion evaluation, traffic signal timing, before and after studies, economic studies
describe six different traffic counting programs
Area wide, Cordon, screenline, TMCs, classification counts, occupancy counts
Find the curve advisory speed for a 30ft radius curve, with a super elevation of 1%, with a side friction factor for 35mph of .15
V=sqrt(15R(.01e+f), where R is the curve radius, e is the superelevation and f is the side friction factor, solving leads to an answer of?
Define travel time
elapsed time of travel
Define running time
time that vehicle is in motion
