Fe Civil Transportation Engineering

Front 1

What is an equivalent single axle load (ESAL)?

Back 1

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.

Front 2

What is a pavement structural number?

Back 2

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.

Front 3

What is a modulus of subgrade reaction?

Back 3

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.

Front 4

What is lateral deflection?

Back 4

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.

Front 5

What is a transportation corridor?

Back 5

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

Front 6

What is an empirical model?

Back 6

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

Front 7

What are empirical models used for?

Back 7

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

Front 8

Why are theoretical models calibrated?

Back 8

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

Front 9

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

Back 9

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

Front 10

What are typical inputs to household worker trip generation?

Back 10

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

Front 11

What are typical inputs to business location trip generation models?

Back 11

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

Front 12

What is time-mean speed?

Back 12

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

Front 13

How does average speed vary with roadway traffic density?

Back 13

This value decreases as roadway traffic density increases.

Front 14

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

Back 14

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

Front 15

What is oversaturation flow?

Back 15

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

Front 16

What is the traffic consequence of mountainous terrain?

Back 16

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

Front 17

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

Back 17

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.

Front 18

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

Back 18

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

Front 19

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

Back 19

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

Front 20

What is an acceleration lane?

Back 20

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

Front 21

What is annual average daily traffic (AADT)?

Back 21

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.

Front 22

What is design hour volume (DHV)?

Back 22

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

Front 23

What is directional design hour volume (DDHV)?

Back 23

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

Front 24

What is directional split?

Back 24

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

Front 25

What is an 85th percentile speed?

Back 25

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.

Front 26

What is free-flow speed (FFS)?

Back 26

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.

Front 27

What is the peak hour factor (PHF)?

Back 27

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.

Front 28

What is a V/C ratio?

Back 28

This is the ratio between the flow rate volume and the capacity of a transportation facility.

Front 29

How is speed limited by geometry?

Back 29

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.

Front 30

What does level of service (LOS) mean?

Back 30

This is a measure of the quality of flow, ranked from A through F, with A being the highest quality.

Front 31

Which LOS is used for maximum capacity?

Back 31

LOS E is used for this capacity.

Front 32

What are three types of traffic signal system controls?

Back 32

Three types of these are pre-timed, semi-actuated and fully-actuated.

Front 33

What is a lane group?

Back 33

This is a set of lanes at an intersection approach that are analyzed together to determine capacity and level of service required.

Front 34

What is a signal cycle?

Back 34

This is a complete sequence of signal phases.

Front 35

How is the base saturation flow rate defined?

Back 35

This is defined as the maximum steady flow rate entering a signalized intersection from the subject approach under ideal conditions.

Front 36

How is saturation flow rate found?

Back 36

This is determined by adjusting the base saturation flow rate by as many as eleven factors that affect the ideal flow rate.

Front 37

What is included in effective green time?

Back 37

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.

Front 38

What is an isolated signalized intersection?

Back 38

This is an intersection that is at least one mile from the nearest upstream signalized intersection.

Front 39

What is a permitted turn?

Back 39

This is a turn at a signalized intersection that is made against an opposing or conflicting vehicle or pedestrian flow.

Front 40

What is a protected turn?

Back 40

This is a turn at a signalized intersection that is made with no opposing or conflicting vehicular or pedestrian flow.

Front 41

What is E_T?

Back 41

This is the symbol for passenger car equivalent for trucks, which can include buses.

Front 42

When is base percent time-spent-following (BPTSF) used?

Back 42

This factor is used in two-lane roadway traffic analysis.

Front 43

What are the two types of development areas used in highway design criteria?

Back 43

These kinds of criteria use rural and urban development areas.

Front 44

What are the three types of terrain used for highway design?

Back 44

Level, rolling, and mountainous are the three types of this.

Front 45

What are two methods of determining earthwork volumes from cross sections?

Back 45

The two methods for determining this are average end area and prismoidal.

Front 46

What is an earthwork mass diagram?

Back 46

This is a plot of cumulative earthwork volume moved along an alignment.

Front 47

What is shown on the x-axis of a mass diagram?

Back 47

Distances in stations are shown on the x-axis of this diagram.

Front 48

What is shown on the y-axis of a mass diagram?

Back 48

The cumulative sum of cut and fill volumes progressing ahead on stationing is shown on the y-axis of this diagram.

Front 49

What is freehaul distance?

Back 49

This is the excavation material haul distance specified in the bid price.

Front 50

What is overhaul?

Back 50

This is the cost of hauling material beyond the freehaul distance.

Front 51

What is the limit of economic haul?

Back 51

This is the distance for which the cost of hauling a unit volume of material is equal to the cost of borrowing it.

Front 52

What is excavation swell?

Back 52

This is the increase in excavated volume over the original in-place volume.

Front 53

What is excavation shrinkage?

Back 53

This is the decrease in excavated volume due to compaction compared to the original in-place volume.

Front 54

Horizontal curves are laid out using what kind of geometry?

Back 54

Circular curves, also called simple curves, are used to lay out this kind of geometry.

Front 55

Vertical curves are laid out using what kind of geometry?

Back 55

Parabolic curves are used to lay out this kind of geometry.

Front 56

How are horizontal distances measured along vertical geometry?

Back 56

These are measured in vertical geometry by projecting curve points to a horizontal plane.

Front 57

How is route geometry measured?

Back 57

This is measured using 100 ft or 100 m stations from an arbitrary starting point.

Front 58

How is a point located that is not exactly on a station?

Back 58

These points are located using the distance from the previous station, which is called a plus.

Front 59

How is a point located that is not on the centerline?

Back 59

These points are located by a radial offset distance from the centerline.

Front 60

How is a horizontal curve stationed?

Back 60

This is stationed from the PC to the PI and from the PC to the PT. The ahead tangent is not stationed.

Front 61

How are direction headings usually shown?

Back 61

These are shown using bearings in the direction of stationing.

Front 62

Circular curves are defined by what two common types of curve definition?

Back 62

These are designed for highways and railroads by arc and chord definitions respectively.

Front 63

What is deflection?

Back 63

This is the angle difference from one curve tangent to the next curve tangent.

Front 64

What is the degree of curve?

Back 64

This is the angle subtended (or deflected) by a 100 ft arc or 100 ft chord.

Front 65

How are vertical grades described?

Back 65

These are described in feet of rise per foot of run, or in percent of rise per unit run.

Front 66

What criteria are used to determine the design superelevation of a curve?

Back 66

The criteria for this are radius, design speed, and the side friction factor.

Front 67

What are the most common ratios of superelevation runoff distance on tangent and in the curve?

Back 67

The most common ratios for this are 2:3 on tangent and 1:3 in the curve.

Front 68

What determines the maximum superelevation rate?

Back 68

This is determined by driver comfort and the side friction required to prevent a stopped vehicle from sliding off the roadway in snow regions.

Front 69

What property of parabolic curves makes them convenient for vertical curve calculations?

Back 69

This kind of curve has vertical offsets from tangent that are proportional squares of the horizontal distance ratio.

Front 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?

Back 70

For a circular curve, this is greater than the middle ordinate, but for a parabolic curve, the middle ordinate and this distance are equal.

Front 71

What are four methods of setting the minimum length of vertical curve for a given speed?

Back 71

The methods for determining this are stopping sight distance, passing sight distance, headlight sight distance, and driver comfort.

Front 72

How does the grade of a vertical parabolic curve change throughout its length?

Back 72

The grade of this curve changes in direct proportion to the distance along the curve.

Front 73

How is superelevation transitioned on a spiraled curve?

Back 73

The length of this kind of curve is used as the superelevation runnout length.

Front 74

How does the degree of curve change along a highway spiral?

Back 74

The degree of this curve changes in direct proportion to the distance along the curve.

Front 75

What is the point where two radii of a compound curve meet called?

Back 75

The point of continuing curve (PCC) is located here.

Front 76

What is the point where two radii of a reverse curve meet called?

Back 76

The point of reverse curve (PRC) is located here.

Front 77

What is a straight line connecting the point of curve (PC) and the point of tangent (PT) called?

Back 77

The long chord connects these points.

Front 78

What feature is necessary to compensate for off-tracking of long wheelbase trucks and buses on curves?

Back 78

Lane widening, or curve widening, compensates for this.

Front 79

What factors are included in stopping distance?

Back 79

Factors for this include perception-reaction time, braking distance, stopping friction factor, and grade.

Front 80

How does grade influence braking distance?

Back 80

Upgrade reduces this distance and downgrade increases this distance.

Front 81

How does tire/pavement friction vary with speed?

Back 81

This friction is reduced at higher speeds.

Front 82

How do antilock braking systems affect braking distance?

Back 82

This kind of braking system results in unchanged or longer braking distances.

Front 83

Is it necessary to superelevate all curves?

Back 83

Broader curves and lower design speeds may not require this.

Front 84

What are the pavement conditions used for AASHTO stopping sight distance tables?

Back 84

Pavement conditions used in these are asphalt or concrete surface, wet roadway, level grade, and average tread depth on tires.

Front 85

What formula is used to determine skidding distance using speed in miles per hour?

Back 85

The equation used to determine this is s = (v^2)/30(f+G)

Front 86

What is the most common way of expressing accident rates?

Back 86

This is the ratio of the number of accidents per year to the number of annual vehicle miles traveled.

Front 87

What is the primary reason that railroad/highway crossings are dangerous?

Back 87

Because railroad vehicles are unable to stop quickly due to low rail/wheel friction, these locations are dangerous.

Front 88

What factors affect the maximum speed on crest vertical curves?

Back 88

Maximum speed is determined here by driver eye height, object height above the roadway, and driver comfort.

Front 89

What factor is usually used to determine the maximum speed on a sag vertical curve?

Back 89

Maximum speed here is determined by headlight sight distance.

Front 90

Why do urban transit buses maneuver slower than automobiles in traffic?

Back 90

Because urban buses frequently have people standing on board, they do this slower than automobiles.

Front 91

What is the most important design factor for reducing accidents on interstate highways?

Back 91

Consistent and uniform design features with no surprises for drivers reduces the number of these.

Front 92

What types of accidents can be reduced by installing intersection traffic signals?

Back 92

Rear-end, right-angle, left-turn, head-on, bicycle-related, and pedestrian-related accidents can be reduced by these.

Front 93

What fixtures are placed in the 30 ft wide clear zone adjacent to open freeway shoulders?

Back 93

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.

Front 94

What do traffic signal warrants cover?

Back 94

These cover minimum traffic on major and minor streets at a crossing, minimum pedestrian volume, minimum gaps, and minimum accident experience.

Front 95

What determines the lettering size and spacing on traffic signs?

Back 95

This is determined by the design speed of the roadway and the viewing distance.

Front 96

What is decision sight distance?

Back 96

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.

Front 97

Why is too much superelevation unsafe?

Back 97

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.

Front 98

What is the basis of crash attenuator design?

Back 98

This is based on maximum survivable deceleration rate that a human body can sustain from a given design speed.