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PTOE Exam Prep > Traffic Operations Analysis > Flashcards

Traffic Operations Analysis Flashcards

1
Q

Flow Rate

A

the number of vehicles that pass a point on a facility per unit of time

when the time unit is one hour or more, the flow rate is referred to as volume

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2
Q

Traffic Demand

A

the number of vehicles desiring to pass that point during the time period

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3
Q

PHF

A

relationship between hourly volume and maximum rate of flow within the hour

PHF = 1.0 - consistent flow
Lower PHF means more extreme peak

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4
Q

Speed

A

distance traveled per unit of time

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5
Q

Time Mean Speed

A

average speed of all vehicles passing a point over a time period

“spot speed”

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6
Q

Space Mean Speed

A

average speed of all vehicles occupying a given section of the roadway over a specific time period

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7
Q

Travel Time

A

the time required to travel a segment of given length

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8
Q

Running Time

A

total time the vehicle is in motion while traversing a segment of a given length

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9
Q

Density

A

number of vehicles in a given length of roadway or a lane

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10
Q

Headway

A

time between successive vehicles passing a point

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11
Q

Spacing

A

distance between successive vehicles passing a point

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12
Q

Equation for uninterrupted flow

A

v = S x D

flow = space mean speed x density

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13
Q

PHF Equation

A

PHF = hourly volume / (4 x peak 15 minute volume)

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14
Q

Capacity

A

ability of a transportation facility or service to meet the quantity of travel demanded by it

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15
Q

Describe uninterrupted flow

A

Vehicles are not interrupted by external factors such as traffic signals, stop/yield signs, or access points.

Freeways and long rural segments between controlled intersections.

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16
Q

Describe interrupted flow

A

Vehicle flow interrupted by factors such as traffic signals, stop/yield signs, frequent intersections/driveways.

Urban streets

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17
Q

Factors that impact capacity

A
  • Lane widths
  • Number and use of lanes
  • Proximity of obstructions along edge of roadway
  • Terrain
  • Type of area (urban, suburban, rural)
  • Vehicle mix (trucks/buses)
  • Driver familiarity
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18
Q

When is No Control an option?

A

Total entering traffic less than 2000 units/day

Adequate approach sight distance

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19
Q

Three levels of traffic control

A

Uncontrolled
Stop or Yield
Signal

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20
Q

When is Yield or Two-Way Stop Control an option?

A

When right-of-way is assigned to the major street and the minor street traffic must stop or yield before proceeding

Total daily traffic on thru street less than 6000 veh/day

Adequate approach sight distance

3 or more crashes susceptible to correction by a stop sign

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21
Q

When should Multi-way Stop Control be considered?

A

As an interim measure where a traffic signal is justified

5 or more crashes in a 12m period are susceptible to correction

Minimum volumes
- 300 veh/hour over 8 hours on major street
- total entering volume 200 units/hr on minor street, with delay of 30 sec/veh during peak hour
- 70% of above if speed >40 mph

22
Q

Steps for capacity analysis at signalized intersections

A

Determine the lane group flow rates
Determine the adjusted saturation flow rate
Determine proportion of traffic arriving on green
Determine capacity
Determine delay
Determine LOS

23
Q

Access management

A

proactive management of vehicular access points to land parcels adjacent to raodways

24
Q

Access management techniques

A

Access spacing
Driveway spacing
Safe turning lanes
Median treatments
Right-of-way management

25
Q

Road diet

A

Reduction in width or number of lanes to reallocate that space for other uses, like bicycle lanes, pedestrian crossing islands, left turn lanes, or parking

26
Q

System Interchange

A

Interchange connecting two freeways, with no at-grade ramp intersections

27
Q

Service Interchange

A

Interchange connecting a higher functional class roadway to a lower functional class roadway, may have at-grade intersections

28
Q

For capacity analysis, freeways are divided into what three parts?

A

Basic Segment
Weaving Area
Ramp Junctions

29
Q

What is freeway capacity under base conditions?

A

2250-2400 passenger cars / hour / lane

30
Q

Base conditions for uninterrupted flow - lane width

A

12’

31
Q

Base conditions for uninterrupted flow - lateral clearance on right side

A

6’

32
Q

Base conditions for uninterrupted flow - vehicle classification

A

All passenger cars

33
Q

Base conditions for uninterrupted flow - driving population

A

commuter-type drivers (familiar with route)

34
Q

Base conditions for uninterrupted flow - terrain

A

Level

35
Q

Base conditions for uninterrupted flow - interchange density

A

2 miles or greater

36
Q

Base conditions for uninterrupted flow - number of lanes in one direction

A

5 or more

37
Q

Steps to calculate LOS

A

Flow Rate > FFS > Density > LOS

38
Q

Free Flow Speed

A

speed of passenger cars measured under low to moderate flow rates

39
Q

Relationship between speed, flow, density

A

v = S x D

D = v / S

40
Q

Factors affecting operations at ramp junctions

A

Peak hour flow rates on mainline and ramp
Length of accel/decel lanes
Geometry, i.e. number of lanes
FFS of mainline and ramp

41
Q

LOS in a weaving area is determined based on…

A

average running speeds
density of all vehicles in segment

42
Q

Recurring Congestion

A

congestion that occurs repeatedly at a certain location during certain times of day

43
Q

Non-recurring Congestion

A

congestion that occurs due to any traffic incident that impacts normal roadway conditions

44
Q

Methods to increase freeway capacity

A

Widen to add lanes
Use shoulders as travel lanes
Reduce lane width to add lanes

45
Q

Improvements to enhance bicycle safety

A

Paved shoulders
Wider outside traffic lanes if no shoulder
Bicycle lanes
Bicycle-safe drainage grates
Maintaining a smooth, clean surface

46
Q

Micro-mobility

A

small, low-speed, human- or electric-powered transportation device

bicycles, scooters, electric scooters, etc.

47
Q

Transportation (Travel) Demand Management

A

influencing people’s travel behavior in such a way that alternative mobility options are presented and/or traffic congestion is reduced

48
Q

Site Specific TDM tools

A

Alternative Modes of Transportation (i.e. ride sharing, carpooling, bicycling)

Alternative Work Hours

Telecommuting

49
Q

Area-wide TDM strategies

A

Growth management through urban design
Congestion pricing
Parking management
Auto restricted zones
Legislation

may include site specific techniques

50
Q

Ramp Metering

A

reduces impacts of merging traffic on mainline traffic flow

51
Q

How do traffic incidents impact the transportation system?

A

Reducing capacity
Increasing delay
Reducing safety

52
Q

Types of managed lanes

A

HOV - preferential treatment for transit, carpools, etc.
HOT - combination of HOV and pricing strategies
Reversible Lanes - accommodate peak direction traffic demand

PTOE Exam Prep (6 decks)

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