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1
Q

What is an equivalent single axle load (ESAL)?

A

This is a standardized traffic load parameter used in designing pavement thickness. It is a loading used to predict a quantity of damage from traffic over the design life of a pavement.

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2
Q

What is a pavement structural number?

A

This value represents the load that a pavement component system can carry. To obtain this value for each layer, a strength coefficient for the material is multiplied by the layer’s thickness.

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3
Q

What is a modulus of subgrade reaction?

A

This is a value that represents the quantity of soil deflection due to a horizontal pressure imposed by a pile. It is used to determine the amount of soil deflection that occurs at a point along the pile installation depth due to horizontal pressure from lateral loading.

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4
Q

What is lateral deflection?

A

This is displacement of the pile in a direction perpendicular to its axis. It is determined using the modulus of subgrade reaction for the soil and the quantity of resulting lateral pressure.

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5
Q

What is a transportation corridor?

A

This is a set of transportation facilities designed for travel between two points.

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6
Q

What is an empirical model?

A

This kind of model is based on a mathematical relationship describing system performance based on statistical analysis of field data.

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7
Q

What are empirical models used for?

A

This kind of model is used to predict the behavior of systems having similar characteristics.

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8
Q

Why are theoretical models calibrated?

A

This is done to theoretical models using real–world data in order to make more accurate predictions.

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9
Q

Planning models assign trips to alternate paths using what two characteristics of the paths?

A

Planning models use the characteristics of distance and time comparisons to assign these.

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10
Q

What are typical inputs to household worker trip generation?

A

The factors for predicting this are: autos owned per household, number of adults employed, household income, proximity to employment, proximity to transit

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11
Q

What are typical inputs to business location trip generation models?

A

The factors for predicting this are: type of business, number of employees, number of customers, square feet of business activity, time of day business activity, proximity to transit

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12
Q

What is time–mean speed?

A

This is the arithmetic average of individual vehicle speeds passing a point on a roadway or lane.

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13
Q

How does average speed vary with roadway traffic density?

A

This value decreases as roadway traffic density increases.

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14
Q

What is the maximum capacity of one lane of freeway under ideal conditions?

A

This freeway condition is 2400 pcphpl (Passenger Cars Per Hour Per Lane)

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15
Q

What is oversaturation flow?

A

This occurs when the arrival flow rate exceeds the capacity rate of flow.

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16
Q

What is the traffic consequence of mountainous terrain?

A

On this kind of terrain, heavy vehicles operate at crawl speeds for significant distances or at frequent intervals, which reduces capacity.

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17
Q

What is the measure of capacity on a highway facility versus a transit facility?

A

Highway facility capacity measures the number of cars per unit time and this other kind of facility capacity measures the number of passengers per unit time.

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18
Q

What is the impact of TSM (Transportation Systems Management) studies?

A

These studies can result in small scale capacity and efficiency improvements.

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19
Q

What are the negative impacts on wetlands caused by transportation projects?

A

The impacts of this kind of project on wetlands include: 1. changing water runoff rates, 2. contamination from spillage from vehicles, 3. contamination from deicing chemicals, 4. reducing the area of wetlands

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20
Q

What is an acceleration lane?

A

This is a paved auxiliary lane that allows vehicles to accelerate before entering the through–traffic lane of a roadway.

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21
Q

What is annual average daily traffic (AADT)?

A

This is the total volume of traffic passing a point or a roadway segment in both directions for one year divided by the number of days in the year.

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22
Q

What is design hour volume (DHV)?

A

This is the traffic volume, expressed in vehicles per hour, for the design hour in both directions.

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23
Q

What is directional design hour volume (DDHV)?

A

This is the traffic volume, expressed in vehicles per hour, for the design hour in the peak direction of flow.

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24
Q

What is directional split?

A

This is the directional distribution of the vehicle volume on a highway expressed as a percentage ratio.

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25
What is an 85th percentile speed?
This is the speed on a highway segment that is exceeded by 15% of the traffic. It is determined by a survey of actual speed counts taken along the subject segment over a period of time.
26
What is free–flow speed (FFS)?
This is the speed used for evaluation of traffic flow on a highway or street segment, which is determined by adjusting BFFS or by on–site speed surveys.
27
What is the peak hour factor (PHF)?
This is the ratio of the total actual hourly volume to the peak 15–min flow rate within the hour. The peak 15–min flow rate is four times the 15–min flow count.
28
What is a V/C ratio?
This is the ratio between the flow rate volume and the capacity of a transportation facility.
29
How is speed limited by geometry?
This is limited by geometry because sight distances and comfort limits are determined by the length and grade change of vertical curves, the radius and superelevation of horizontal curves, and sight distance clearances around obstructions.
30
What does level of service (LOS) mean?
This is a measure of the quality of flow, ranked from A through F, with A being the highest quality.
31
Which LOS is used for maximum capacity?
LOS E is used for this capacity.
32
What are three types of traffic signal system controls?
Three types of these are pre–timed, semi–actuated and fully–actuated.
33
What is a lane group?
This is a set of lanes at an intersection approach that are analyzed together to determine capacity and level of service required.
34
What is a signal cycle?
This is a complete sequence of signal phases.
35
How is the base saturation flow rate defined?
This is defined as the maximum steady flow rate entering a signalized intersection from the subject approach under ideal conditions.
36
How is saturation flow rate found?
This is determined by adjusting the base saturation flow rate by as many as eleven factors that affect the ideal flow rate.
37
What is included in effective green time?
This includes the green time for that movement plus a portion of the yellow time while the traffic still moves through the intersection, minus the first portion of green time before the traffic begins to move. It is equal to the cycle length minus the effective red time.
38
What is an isolated signalized intersection?
This is an intersection that is at least one mile from the nearest upstream signalized intersection.
39
What is a permitted turn?
This is a turn at a signalized intersection that is made against an opposing or conflicting vehicle or pedestrian flow.
40
What is a protected turn?
This is a turn at a signalized intersection that is made with no opposing or conflicting vehicular or pedestrian flow.
41
What is E_T?
This is the symbol for passenger car equivalent for trucks, which can include buses.
42
When is base percent time–spent–following (BPTSF) used?
This factor is used in two–lane roadway traffic analysis.
43
What are the two types of development areas used in highway design criteria?
These kinds of criteria use rural and urban development areas.
44
What are the three types of terrain used for highway design?
Level, rolling, and mountainous are the three types of this.
45
What are two methods of determining earthwork volumes from cross sections?
The two methods for determining this are average end area and prismoidal.
46
What is an earthwork mass diagram?
This is a plot of cumulative earthwork volume moved along an alignment.
47
What is shown on the x–axis of a mass diagram?
Distances in stations are shown on the x–axis of this diagram.
48
What is shown on the y–axis of a mass diagram?
The cumulative sum of cut and fill volumes progressing ahead on stationing is shown on the y–axis of this diagram.
49
What is freehaul distance?
This is the excavation material haul distance specified in the bid price.
50
What is overhaul?
This is the cost of hauling material beyond the freehaul distance.
51
What is the limit of economic haul?
This is the distance for which the cost of hauling a unit volume of material is equal to the cost of borrowing it.
52
What is excavation swell?
This is the increase in excavated volume over the original in–place volume.
53
What is excavation shrinkage?
This is the decrease in excavated volume due to compaction compared to the original in–place volume.
54
Horizontal curves are laid out using what kind of geometry?
Circular curves, also called simple curves, are used to lay out this kind of geometry.
55
Vertical curves are laid out using what kind of geometry?
Parabolic curves are used to lay out this kind of geometry.
56
How are horizontal distances measured along vertical geometry?
These are measured in vertical geometry by projecting curve points to a horizontal plane.
57
How is route geometry measured?
This is measured using 100 ft or 100 m stations from an arbitrary starting point.
58
How is a point located that is not exactly on a station?
These points are located using the distance from the previous station, which is called a plus.
59
How is a point located that is not on the centerline?
These points are located by a radial offset distance from the centerline.
60
How is a horizontal curve stationed?
This is stationed from the PC to the PI and from the PC to the PT. The ahead tangent is not stationed.
61
How are direction headings usually shown?
These are shown using bearings in the direction of stationing.
62
Circular curves are defined by what two common types of curve definition?
These are designed for highways and railroads by arc and chord definitions respectively.
63
What is deflection?
This is the angle difference from one curve tangent to the next curve tangent.
64
What is the degree of curve?
This is the angle subtended (or deflected) by a 100 ft arc or 100 ft chord.
65
How are vertical grades described?
These are described in feet of rise per foot of run, or in percent of rise per unit run.
66
What criteria are used to determine the design superelevation of a curve?
The criteria for this are radius, design speed, and the side friction factor.
67
What are the most common ratios of superelevation runoff distance on tangent and in the curve?
The most common ratios for this are 2:3 on tangent and 1:3 in the curve.
68
What determines the maximum superelevation rate?
This is determined by driver comfort and the side friction required to prevent a stopped vehicle from sliding off the roadway in snow regions.
69
What property of parabolic curves makes them convenient for vertical curve calculations?
This kind of curve has vertical offsets from tangent that are proportional squares of the horizontal distance ratio.
70
What is the difference between the middle ordinate and external distances of a circular curve as opposed to the difference in a parabolic curve?
For a circular curve, this is greater than the middle ordinate, but for a parabolic curve, the middle ordinate and this distance are equal.
71
What are four methods of setting the minimum length of vertical curve for a given speed?
The methods for determining this are stopping sight distance, passing sight distance, headlight sight distance, and driver comfort.
72
How does the grade of a vertical parabolic curve change throughout its length?
The grade of this curve changes in direct proportion to the distance along the curve.
73
How is superelevation transitioned on a spiraled curve?
The length of this kind of curve is used as the superelevation runnout length.
74
How does the degree of curve change along a highway spiral?
The degree of this curve changes in direct proportion to the distance along the curve.
75
What is the point where two radii of a compound curve meet called?
The point of continuing curve (PCC) is located here.
76
What is the point where two radii of a reverse curve meet called?
The point of reverse curve (PRC) is located here.
77
What is a straight line connecting the point of curve (PC) and the point of tangent (PT) called?
The long chord connects these points.
78
What feature is necessary to compensate for off–tracking of long wheelbase trucks and buses on curves?
Lane widening, or curve widening, compensates for this.
79
What factors are included in stopping distance?
Factors for this include perception–reaction time, braking distance, stopping friction factor, and grade.
80
How does grade influence braking distance?
Upgrade reduces this distance and downgrade increases this distance.
81
How does tire/pavement friction vary with speed?
This friction is reduced at higher speeds.
82
How do antilock braking systems affect braking distance?
This kind of braking system results in unchanged or longer braking distances.
83
Is it necessary to superelevate all curves?
Broader curves and lower design speeds may not require this.
84
What are the pavement conditions used for AASHTO stopping sight distance tables?
Pavement conditions used in these are asphalt or concrete surface, wet roadway, level grade, and average tread depth on tires.
85
What formula is used to determine skidding distance using speed in miles per hour?
The equation used to determine this is s = (v^2)/30(f+G)
86
What is the most common way of expressing accident rates?
This is the ratio of the number of accidents per year to the number of annual vehicle miles traveled.
87
What is the primary reason that railroad/highway crossings are dangerous?
Because railroad vehicles are unable to stop quickly due to low rail/wheel friction, these locations are dangerous.
88
What factors affect the maximum speed on crest vertical curves?
Maximum speed is determined here by driver eye height, object height above the roadway, and driver comfort.
89
What factor is usually used to determine the maximum speed on a sag vertical curve?
Maximum speed here is determined by headlight sight distance.
90
Why do urban transit buses maneuver slower than automobiles in traffic?
Because urban buses frequently have people standing on board, they do this slower than automobiles.
91
What is the most important design factor for reducing accidents on interstate highways?
Consistent and uniform design features with no surprises for drivers reduces the number of these.
92
What types of accidents can be reduced by installing intersection traffic signals?
Rear–end, right–angle, left–turn, head–on, bicycle–related, and pedestrian–related accidents can be reduced by these.
93
What fixtures are placed in the 30 ft wide clear zone adjacent to open freeway shoulders?
Frangible bases on roadside luminaires and signs, drainage fixtures that are flush with the ground and that will support wheel loads, and ditches with broad–sloped sides are all placed here.
94
What do traffic signal warrants cover?
These cover minimum traffic on major and minor streets at a crossing, minimum pedestrian volume, minimum gaps, and minimum accident experience.
95
What determines the lettering size and spacing on traffic signs?
This is determined by the design speed of the roadway and the viewing distance.
96
What is decision sight distance?
This is the distance needed for a driver to detect an unexpected or otherwise difficult to perceive condition on a roadway and to select an appropriate maneuver.
97
Why is too much superelevation unsafe?
Too much of this can cause drivers and passengers to become disoriented, large trucks to tip over at low speed, and vehicles to slide off of the road at low speed where ice occurs.
98
What is the basis of crash attenuator design?
This is based on maximum survivable deceleration rate that a human body can sustain from a given design speed.

Transportation Engineering (5 decks)

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