Definitions.
Capacity
The maximum number of vehicles that can pass a given point
under prevailing roadway and traffic conditions. Capacity represents
the ability of a roadway or an intersection to accommodate the vehicular
demand.
Crash Analysis
A summary of the crash history at nearby intersections and
on adjacent roadways during a specified time period. Crash trends
and contributing factors are identified, where present. Where site
traffic is anticipated to contribute to or exacerbate an identified
crash trend or safety issue, measures to mitigate or reduce the propensity
for crashes should be included in the TIA.
Level of Service (LOS)
A qualitative measure of traffic operating conditions based
on equations utilizing quantitative values. Level of service (LOS)
describes the quality of traffic operating conditions and is rated
from "A" to "F". LOS A represents the most desirable condition with
the free-flow movement of traffic with minimal delays. LOS F generally
indicates severely congested conditions with excessive delays to motorists.
Intermediate grades of B, C, D, and E reflect incremental increases
in the average delay per stopped vehicle. Delay is measured in seconds
per vehicle.
Level of Service analyses conducted as part of a TIA shall
be determined using procedures of the latest edition of the Highway
Capacity Manual, Special Report 209 published by the Transportation
Research Board (TRB).
Modal Split
The percentage of trips by mode. For example, bicycle, walking,
single-occupant automobile, shared ride or transit.
Queue Length Analysis
An analysis of vehicle stacking/queueing and identification
of the needed lane storage necessary to accommodate anticipated maximum
vehicle queues. Typically performed for drive-through facilities,
drop-off zones to schools and day care facilities.
Sight Distance Evaluation
An evaluation of the available horizontal and vertical sight
distance for entering and exiting traffic movements at access points
to a site, intersection, or roadway section.
Signal Cycle Length
The time period, in seconds, required for one complete sequence
of traffic signal indications.
Signal Phase
A part of the signal cycle allocated to a traffic movement
or any combination of traffic movements.
TIA
A study that provides information to:
1.
Identify impacts to the road network, created by the traffic
generated by a proposed development; and
2.
Determine whether the existing and planned thoroughfare system
can accommodate the traffic to be generated by a proposed development;
and
3.
Identify and evaluate the appropriate improvements and recommendations
needed to mitigate the impacts from the development.
TIA Analysis Periods
The designated time periods to be studied and analyzed for
assessment of traffic operations as part of a TIA submittal.
Traffic Control Device
Signs, signals, pavement markings, or device placed or erected
for the purpose of regulating, warning, guiding, or restricting vehicular
traffic or pedestrians.
Traffic Simulation
The use of a computer model to provide detailed analysis
of the interaction between traffic, roadway geometry, and traffic
control devices.
Trip Distribution
The distribution of estimated peak hour trips generated by
the proposed development onto the street system using existing traffic
patterns, demographic data, and travel characteristics of land uses.
Trip Generation
The estimated number of trips, entering and exiting, generated
by proposed land uses and based on variables that may include building
size, type of dwelling unit, employees, land area, etc. Trip generation
calculations are typically based on statistical data in the ITE Trip
Generation publication or through collection of trip data at similar
land uses.
Turn Lane Analysis
A determination of the need for turn lanes and an analysis
of storage requirements combined with acceleration/deceleration length
requirements for driveways, median openings and intersections based
on existing and future roadway volumes, geometry, speeds and traffic
controls. The City of Bee Cave utilizes the TxDOT Roadway Design Manual
and Access Management Manual for turn lane standards.
Volume/Capacity Ratio (V/C)
The ratio of daily or peak hour traffic volume to the capacity
of a roadway, lane or intersection. A V/C at or over 1, represents
an over-saturated condition where the capacity of the roadway, lane
or intersection exceeds the demand and fails to operate effectively.