traffic engineering: traffic characteristics Flashcards
What are the 3 main categories of traffic studies?
- inventories
- administrative studies
- dynamic studies
_____ provide a list or graphic display of existing information, such as street widths, parking spaces, transit routes, traffic regulations, adn so forth.
inventories
____ use existing engineering records, available in government agencies and departments.
administrative studies
____ include the results of surveys, which may involve field measurements and/or aerial photogrpahy.
administrative studies
____ involve the collection of data under operational conditions and include studies of speed, traffic volume, travel time and delay, parking, and crashes.
dynamic studies
What are the 4 studies under dynamic traffic studies?
- spot speed studies
- volume studies
- travel time and delay studies
- parking studies
_____ are conducted to estimate the distribution of speeds of vehicles in a stream of traffic at a particular location on a highway.
spot speed studies
The ____ is defined as the rate of movement of the vehicle.
speed of the vehicle
A ____ is carried out by recording the speeds of a sample vehicle at a specified location.
spot speed study
Speed limits (___th-percentile speeds is commonly used as the speed limit on the road).
85
What are the 3 locations for spot speed studies?
- locations that represent different traffic conditions (basic data collection)
- mid-blocks of urban highways and straight (speed trend analysis)
- any location (specific traffic engineering problem)
The time of day for conducting a speed study depends on the _____.
purpose of the study
To establish posted speed limits, to observe speed trends, or to collect basic data – conduct study when
traffic is free-flowing usually during off-peak hours
Conducted in response to citizen complaints, it is useful if the time period selected for the study _____
reflects the nature of the complaints
Typically, the duration is at least ___ and the sample sample size is at least ___ vehicles.
1 hour, 30
The ____ (or average) speed is used to represent the true mean value of all vehicle speeds at that location.
calculated mean
The larger the sample size (number of vehicles), the ____ the probability that the estimated mean is not significantly different from the true mean.
greater
____ are used to determine this minimum sample size.
statistical procedures
What are the 6 significant values needed to described speed charactersitcs?
- average speed
- median speed
- modal speed
- the ith-percentile spot speed
- pace
- standard deviation of speeds
____ is the arithmetic mean of all observed vehicle speeds (which is the sum of all spot speeds divided by the number of recorded speeds).
average speeds
____ which is the range of speed–usually taken at 10-mi/h intervals–that has the greatest number of observations.
pace
____ which is a measure of the spread of the individual speds.
standard deviation of speeds
What are the 2 main categories of conducting spot speed studies?
- manual
- automatic
What are the 3 manual devices?
- stopwatch
- radar gun
- lidar gun
What are the 3 automatic devices?
- those that use road detectors (pneumatic road tubes, inductive loop)
- those that are radar-based (radar recorders)
- those that use the principles of electronics (autoscope)
____ is wireless detector with a single camera that can replace many loops, thereby providing a wide-area detection system.
autoscope
____ work on the principle that when a signal is transmitted onto a moving vehicle, the change in frequency between the transmitted signal and the reflected signal is proportional to the speed of the moving vehicle.
radar recorders
____ laid across the lane
pneumatic road tube
____ are conducted to collect data on the number of vehicles and/or pedestrians that pass a point on a highway facility during a specified time period.
traffic volume studies
Traffic volume studies time period varied from as little as ____ to as much as ___ depending on the anticipated use of the data.
15 minutes - 1 year
The data collected from traffic volume studies may also be put into 4 subclasses:
- directional movement
- occupancy rates
- vehicle classification
- pedestrian age
____ are usually conducted when certain volume characteristics are needed.
traffic volume studies
What are the 5 volume characteristics?
- average annual daily traffic (AADT)
- average daily traffic (ADT)
- peak hour volume (PHV)
- vehicle classification (VC)
- vehicle miles of travel (VMT)
_____ is the average of 24-hour counts collected every day of the year.
average annual daily traffic (AADT)
__ is the average of 24-hour counts collected over a number of days greater than one but less than a year.
average daily traffic (ADT)
What are the 3 which ADT may be used for?
- planning of highway activities
- measurement of current demand
- evaluation of existing traffic flow
___ is the maximum number of vehicles that pass a point on a highway during a period of 60 consecutive minutes.
peak hour volume (PHV)
____ records volume with respect to the type of vehicles, for example, passenger cars, two-axle trucks, or three-axle trucks.
vehicle classification (VC)
____ is a measure of travel along a section of road.
vehicle miles of travel (VMT)
____ is the product of the traffic volume (that is, average weekday volume or ADT) and the length of raodway in miles to which the volume is applicable.
vehicle miles of travel (VMT)
____ are used mainly as a base for allocating resources for maintenance and improvement of highways.
VMT
What are the 2 methods of conducting volume count?
- manual method
- automatic method
___ involves one or more persons recording observed vehicles using a counter.
manual counting
With the manual counting method, both the ____ at the intersection and the ___ can be recorded.
turning movement, types of vehicles
What are the 3 main disadvantages of the manual count method?
- labor intensive; thus expensive
- subject to the limitations of human factors
- cannot be used for long periods of counting
What are the 2 categories of automatic counters?
- require the laying detectors (surface or subsurface)
- do not require the laying of detectors