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Route > Midterm 2 > Flashcards

Midterm 2 Flashcards

1
Q

series of 2 or more circular curves; any 2 successive curves having a common tangent

A

compound curves

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2
Q

3 things that “define”a compound curve?

A
  1. ) Simple Curve
  2. ) Curvature in the same direction
  3. ) Common Tangent
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3
Q

where are compound curves used?

A

at grade intersections, highway sections in difficult topography, and ramps of interchanges, to avoid obstacles

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4
Q

ratio of compound curves for highways

A

1.5:1

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5
Q

two simple curves with equal radii turning in opposite directions with a common tangent

A

reverse curves

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6
Q

What is the purpose of reverse curves?

A

to change the alignment of the highway, to redirect through lanes at channelized intersections and high speed median crossovers

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7
Q

What is one downfall of reverse curves?

A

Causes sudden change in alignment which makes it hard to stay in lane

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8
Q

Why is vertical alignment important

A

to determine the elevation to ensure proper drainage, and an acceptable level of safety and comfort

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9
Q

What is the primary challenge of vertical curves?

A

Transitioning from one grade to another

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10
Q

two types of vertical curves

A

crest and sag

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11
Q

True or false: vertical curves have equal tangents making it symmetrical about the PVI

A

true

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12
Q

What type of shape do vertical curves most mimic, circular or parabolic?

A

Parabolic

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13
Q

how are grades selected?

A

based on the type of urban or rural, type of street, and design speed

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14
Q

location at which the curve is level/where the slope is zero

A

turning points

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15
Q

why are turning points important?

A

Water can collect

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16
Q

number of horizontal feet needed for a 1% change in the slope; also known as vertical curvature

A

k factor

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17
Q

what can the k factor be used for?

A

Finding high/lowpoints

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18
Q

What is the goal of SSD considerations?

A

to find an appropriate length (L) for the curve that can accommodate the correct SSD

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19
Q

Advantages of transition curve advantages

A

appearance of the highway is enhanced, reduces break in alignment, suitable zone for super elevation runoff

20
Q

curves placed between tangent and circular sections of roadway; beginning with an infinite radius to match the tangent ending with the same radius as the curveS

A

transition curves

21
Q

Curve where the radius is infinite at the tangent end and radius of circular curve at the other end

A

Spiral Curve

22
Q

Where can spiral curves be located

A

approaching a curve, leaving a curve, connect two circular curves of differential radii

23
Q

does the central angle change when reducing to a spiral curve?

A

no but the curve angle gets reduced by -2delta

24
Q

General types of roadways

A

divided and undivided

25
Q

types of undivded roadways

A
  1. ) 2-lane undivided
  2. ) 3-lane undivided
  3. ) multi-lane undivided
26
Q

types of divided roadways

A

multi-lane divided

27
Q

number of lanes eq

A

DDHV/SFL

28
Q

what does lane width depend on

A

classification, volume, design speed

29
Q

how do you widen the pavement for simple curves?

A

widen the inside edge of traveled way only

30
Q

how to widen pavement for spiral curves

A

widen inside edge of traveled way; mark centerline midway between edges of pavement

31
Q

what is the cross slope used for?

A

necessary for proper drainage; prevents ponding on surface, determined on construction technologies, materials and equipment

32
Q

provided along the road edge to serve as an emergency lane for vehicles

A

shoudlers

33
Q

normal width of shoulder

A

10’

34
Q

portion of highway separating opposing directions of travel; dimenson between the edges of traveled way; includes shoulder width

A

median

35
Q

three types of medians

A

raised, depressed, flush

36
Q

widths of medians

A

4-84 feet

37
Q

where are median openings and what do they do?

A

3 mile intervals; provide u turn capabilities

38
Q

how much feet permits recovery of vehicles

A

30 feet

39
Q

What is a clear zone based on

A

volumes, speed, roadside slopes

40
Q

How does a curve clear zone vary?

A

you must provide 50% more Clear zone

41
Q

what do you place on shoulder if clearzone obstructions are not removable?

A

guardrails

42
Q

the boundaries between the pavement and shoulders/footpath

A

curbs

43
Q

designates traveled way cross section used on curves

A

normal crown

44
Q

between normal crown and full superelevated

A

reverse adverse crown

45
Q

super elevation transition =

A

tangent runout to superelevation run off

46
Q

gradual change from crown normal to a point where the adverse cross slope is removed

A

tangent runout

47
Q

gradual change from end of tangent runout to a cross section that is fully superelevated

A

superelevation runoff

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