p

people, person, or pedestrian

ln

lane

pcph

passenger cars per hour

pcphg

passenger cars per hour of green signal

pcphpl

passenger cars per hour per lane

pcphgpl

passenger cars per hour of green signal per lane

pc

passenger car

pc / km / ln

passenger cars per kilometer per lane

pcpmpl

passenger cars per mile per lane

veh

vehicle

vph

vehicle per hour

vph / lane

vehicles per hour per lane

pers

person

ped

pedestrian

vpm

vehicles per mile

vpk

vehicles per kilometer

DDHV

Directional Design Hourly Volume

According to AASHTO GDHS-7, what are the four (4) general classes of design vehicles?

1. passenger cars

2. buses

3. trucks

4. recreational vehicles

In addition, the bicycle should also be considered as a design vehicle where bicycle use is anticipated on a roadway. Refer to the AASHTO Guide for the Development of Bicycle Facilities (7) for a discussion of bicycle dimensions and bicyclist operating space.

The passenger-car design class includes which type of vehicles?

The passenger-car class includes passenger cars of all sizes, 

sport / utility vehicles, minivans, vans, and pick-up trucks.

The buses design class includes which type of vehicles?

The bus design class includes intercity (motor coach-es), city transit, school, and articulated buses.

The truck design class includes which type of vehicles?

The truck class includes single-unit trucks, truck tractor semitrailer combinations, and truck tractors with semitrailers in combination with full trailers.

The recreational vehicle design class includes which type of vehicles?

The recreational vehicle design class includes motor homes, cars with camper trailers, cars with boat trailers, motor homes with boat trailers, and motor homes pulling cars.

Which table in the Green Book provides dimensions as well as the wheelbase for twenty (20) design vehicles representing motor vehicles within the general classes?

Table 2-4

AASHTO GDHS-7 

Which table in the Green Book provides the minimum turning radii for twenty (20) design vehicles representing motor vehicles within the general classes?

Table 2-5

AASHTO GDHS-7

Which figures in the Green Book provides the minimum turning paths for twenty (20) design vehicles representing motor vehicles within the general classes?

Figures 2-10 through 2-18 and 2-22 through 2-32

AASHTO GDHS-7

The time required to respond successfully to any driving situation, such as an emergency, involves these four stages: 

1. Perception (detection and identification)

2. Decision

3. Reaction

4. Response of the vehicle

What is the design standard for PRT used by AASHTO?

The PRT used for design standards by AASHTO includes 1.5 seconds for perception and decision, 1.0 seconds for making a response, for a total of 2.5 seconds, which is generally considered adequate for all but the most complex driving situations. 

Determining service flow rate of a roadway requires which of the following criteria, according to the HCM?

I.         driver population factor

II.       heavy vehicle factor

III.      lane width factor

IV.       number of lanes

V.        parking adjustment factor

VI.      peak hour factor

VII.     average control delay per vehicle

VIII.    volume-over-capacity ratio

(A) I, II, IV, and VI

(B) I, II, IV, and VIII

(C) I, II, III, IV and V

(D) II, III, V, VI and VII

(A) I, II, IV, and VI

What is the concept of Perception-Reaction Time (PRT)?

PRT is “the interval between the appearance of some object or condition in the driver’s field of view and the initiation of a response” such as braking or changing course. Note that PRT involves the initiation of a response (e.g. pressing the brake), not the completion of the vehicle maneuver (stopping). 

SMS

Space Mean Speed

What is the definition of the term Space Mean Speed (SMS)?

Average speed of all vehicles occupying a given section of roadway over a specific time period. Note the variable S is also used to represent Space Mean Speed (SMS).

TMS

Time Mean Speed

What is the definition of the term Time Mean Speed (TMS)?

Average speed of all vehicles passing a point over a specified time period.

What is the equation used to calculate the maximum flow rate (V_p)?

V_p = V / PHF

V_p = maximum flow rate 

V = peak arrival of cars (vph)

PHF = peak hour factor

How many cars can a four (4) way stop handle?

1600 vph - 1800 vph

What is a downside of using a traffic signal?

Pressure on the Traffic Engineer to time the signal correctly.

When a traffic signal is put in a flashing operation, which of the following statements is FALSE?

(A) A yellow indication should be used for the major street, and a red indication should be used for all other approaches

(B) Each approach or separate controlled turn movement shall be provided with a flashing display.

(C) Protected or protected / permissive left-turn movements shall flash red when the through movement flashes yellow.

(D) The most restrictive minor street should have a red indication, and all approaches may have a yellow indication.

To avoid a possible moving conflict or collision, all signal faces should flash red, meaning all approaching traffic to stop. Alternatively, a flashing yellow can be used for the major movement and for any nonconflicting turn movements that have adequate sight distance to proceed without coming to a full stop. It is unsafe to have more than one approach with yellow indication.

(D) The most restrictive minor street should have a red indication, and all approaches may have a yellow indication.

What is the equation used to calculate the number of lanes (n) required?

n = V_p / μ

n = number of lanes

V_p = maximum flow rate

μ = service rate

DHV

Design Hourly Volume

What is the definition of Design Hour Volume (DHV)?

DHV is the 30^th highest hourly volume expected over an year (two-way unless noted).

What is the equation used to calculate the Directional Design Hour Volume (DDHV)?

DDHV = D * DHV * = D * K * AADT

DDHV = directional design hour volume

D = directional factor

K = factor

AADT = average annual daily traffic

ADT

Average Daily Traffic (one-way or two-way)

AADT

Average Annual Daily Traffic (one-way or two-way)

What are the equations used to calculate the Average Annual Daily Traffic (AADT)?

AADT = Total Yearly Volume / 365

AADT = 24-hour count on a particular day * daily variation factor * monthly variation factor 

What is the equation used to calculate the Design Hour Volume (DHV)?

DHV = K * AADT

DHV = design hour volume

K = factor

AADT = average annual daily traffic

What is the definition of Headway?

Headway is the time between successive vehicles (sec/veh).

What are the equations used to calculate Headway?

Headway = 3600 (sec/hr) / V

Headway = Spacing / SMS

V =

SMS = space mean speed (sometimes give as S)

What is the definition of Spacing?

Spacing is the distance between common points (e.g. the front bumper) on successive vehicles (ft/veh).

What is the equation used to calculate Spacing?

Spacing (ft) = 5,280 (ft/mile) / D

D = density (vpmpl)

What are the four (4) volumes of the Highway Capacity Manual (HCM)?

1. Concepts

2. Uninterrupted flow

3. Interrupted flow

4. Applications Guide

What are the equations of motion (constant acceleration)?

1. x = vt

2. v = v₀ + at

3. x = v₀t + (1/2)at²

4. v² = v₀² + 2ax

Crash rates for intersections are normally expressed in terms of crashes per million entering vehicles (MEV), using the which equation?

R_int = A * 10⁶ / (365 * T * V)

R_int = crash rate for the intersection

A = number of reported crashes

T = time period of the analysis (years)

V = average daily traffic (ADT) volumes entering the intersection (veh/day)

Crash rates for roadway segments are normally expressed in terms of crashes per 100 million vehicle-miles (100 MVM), using which equation?

R_int = A * 10⁸ / (365 * T * V * L)

R_sec = crash rate for the roadway section

A = number of reported crashes

T = time period of the analysis (years)

V = average daily traffic (ADT) volumes (veh/day)

L = length of the segment (miles)

At High Street and Main Street intersection there were 3 fatalities in 28 total accidents in the last three years. What is the severity index (SI)? 

SI = fatalities / total accidents

SI = 3 / 28 = 0.107 deaths / accident