1. Curves, island,
interchanges and
freeway
REPORTED BY:
JOSEPH R.
POLICENA

2. Table of content
 Widening of curves
 Islands
 Island is included in the design by the ff purposes
 Interchange
 Function of freeway interchanges
 Types of interchange
 Four-way interchanges
 three-way interchanges
 two-way interchanges
 Freeway entrance and exit
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3. Widening of curves
Page 3

4. Provision for a wider roadway is necessary on
sharp curve for two lanes pavement under the ff.
reason
1. To force the drivers to
shy away from the
pavement edge.
2. To increase the
effective transverse
vehicle width for non-
tracking of front and
rear wheel. Page 4

5. Provision for a wider roadway is necessary on
sharp curve for two lanes pavement under the ff.
reason
3. To give additional width due
to the slanted position of the
front wheel to the roadway
center line.
4. For a 7.2m wide roadway, an
additional width of 30cm is
necessary on an open curve
highway.
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6. Islands
 Is a define area between
traffic lanes for controls of
vehicle movement and for
pedestrian refuge. Within an
intersection, median is
considered as an island.
Page 6

7. Island is included in the design by the ff
puRposes
1. Separation of vehicles flow
2. Separation of conflicts
3. Reduction in excessive
pavement areas
4. Reduction of traffic and
indications of proper use of
intersection
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8. Island is included in the design by the ff
puRposes
5. Arrangement to favor a
prominent turning movement
6. Location to traffic control
devices
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9. General types and shapes
of an island
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10. General types and shapes
of an island
Page 10

11. General types and shapes
of an island
Page 11

12. Interchange
 a road junction that typically
uses grade separation, and
one or more ramps, to permit
traffic on at least one highway
to pass through the junction
without directly crossing any
other traffic stream. It differs
from a standard intersection,
at which roads cross at grade.
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13.  The High Five in Dallas, Texas, USA:
an extreme example of interchange design. This is a complicated five-level stack Page 13
interchange due to the proximity of frontage roads.

14. Function of freeway
interchanges
 To provide separation
between two or more traffic
arteries.
 To facilitate easy transfer of
vehicles from one entry to the
other or between local
roadways and the freeway.
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15. Use of overpass or underpass?
 UNDERPASS
 Depends on topography,
economy and any other minor
factors
 Underpass better for
deceleration/acceleration, cost
and advance warning
 OVERPASS
 Overpass better aesthetics Page 15

16. Types of interchange
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17. Four way interchanges
1. Cloverleaf interchange –
 typically a two-level, four-way
interchange where all left turns are
handled by loop ramps (right turns
if traveling on the left).
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18.  A typical cloverleaf interchange in
Ohio, United States
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19. Advantage of cloverleaf
 they require only one bridge,
which makes such junctions
inexpensive as long as land is
plentiful
 A major shortcoming of
cloverleafs, however, is
weaving and the consequent
low capacity of this design.
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20. Objections to the cloverleaf
interchange design
 It requires large area of land
 At higher design speed, more
time is consumed just to
transverse the longer loops
 Vehicles making left turn execute
270° right turn and travel greater
distance becoming very
unpleasant and hazardous due to
sharp curves and steep grades.
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21. Objections to the cloverleaf
interchange design
 Vehicles leaving the curve
loop in one quadrant weave
those entering the adjacent
loop from the through road
way.
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22. Four way interchanges
2. Stack interchange –
 whereby left turns are
handled by semi-
directional flyover/under
ramps.
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23.  A multi-level stack interchange
in Shanghai, China
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24. Disadvantages
 Expensive
 creates an eyesore among
local residents, leading to
considerable (Not In My Back
Yard) opposition
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25. Four way interchanges
3. Cloverstack interchange –
 Its ramps are longer to allow for
higher ramp speeds, and loop
ramp radii are made larger as well.
The large loop ramps eliminate the
need for a fourth, and sometimes
a third level in a typical stack
interchange, as only two directions
of travel use flyover/under ramps.
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26. 1st level 2nd level
1st level
3rd level
2nd level
Two way cloverstack Three way cloverstack
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27. advantages
 cheaper to build than stack
interchanges
 less of an eyesore for local
residents
 weaving is also eliminated
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28. disadvantages
 require a lot of land to
construct
 the loop ramps are not as
efficient as flyover/under
ramps in terms of traffic flow
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29. Four way interchanges
4. Turbine interchange (whirlpool)
 requires fewer levels (usually two
or three) while retaining semi-
directional ramps throughout, and
has its left-turning ramps sweep
around the center of the
interchange in a spiral pattern in
right-hand driving.
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30.  The Circle Interchange in Chicago, a notable
turbine interchange
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31. 2nd level
2nd level 3rd level
1st level 1st level
Two way turbine Three way turbine
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32. Four way interchanges
5. Roundabout interchange –
 The ramps of the interchanging
highways meet at a roundabout or
rotary on a separated level above,
below, or in the middle of the two
highways.
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33. Page 33

34. Other/hybrid interchanges
1. windmill interchange
 is similar to a turbine
interchange, but it has
much sharper turns,
reducing its size and
capacity
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35. Page 35

36. Other/hybrid interchanges
2. diverging windmill
 increases capacity by
altering the direction of
traffic flow of the
interchanging highways,
making the connecting
ramps much more
direct.
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37. Page 37

38. Other/hybrid interchanges
3. Divided volleyball
 create a wide median
between the
carriageways of the two
interchanging highways,
using this space for
connecting ramps.
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39. Page 39

40. Other/hybrid interchanges
4. Full diamond
 large, multi-level
interchanges that use
flyover/under ramps to
handle both right and
left ramps.
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41. Page 41

42. Hybrid interchange near Rotterdam,
Netherlands.
Hybrid interchange near
Cross-Harbour Tunnel,
Hong Kong.
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43. Three way interchanges
 Trumpet interchange
 have been used where one highway
terminates at another highway. These
involve at least one loop ramp
connecting traffic either entering or
leaving the terminating expressway
with the far lanes of the continuous
highway.
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44. A trumpet interchange on the
Ottawa River Parkway
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45. Three way interchanges
 Directional T interchange
 uses flyover/under ramps in all
directions at a three-way
interchange. A semi-directional T
does the same, but some of the
splits and merges are switched to
avoid ramps to and from the
passing lane.
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46. Semi-directional-T
interchange in Lausanne,
Switzerland Page 46

47. Three way interchanges
 Full Y interchange
 typically used when a three-way
interchange is required for two or three
highways interchanging in semi-
parallel/perpendicular directions, but it
can also be used in right-angle case as
well. Their connecting ramps can spur
from either the right or left side of the
highway, depending on the direction of
travel and the angle. Page 47

48. Page 48

49. Two way interchanges
 Diamond interchange
 interchange involving four ramps
where they enter and leave the
freeway at a small angle and
meet the non-freeway at almost
right angles.
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50. Page 50

51. Diamond interchange in Ohio, United
States
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52. Two way interchanges
 Parclo interchange/folded
diamond
 also known as a partial
cloverleaf, is an interchange
usually involving four to six
ramps, two of which are loop
ramps, which connect to the
non-highway.
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53. Page 53

54. Parclo A-4 interchange in
Ontario, Canada.
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55. Two way interchanges
 Diverging diamond interchange
 similar to a traditional diamond
interchange, except that it uses
directional lanes for the non-highway
to cross over each other on either
side of the highway, altering the
direction of travel on the
over/underpass through the use of
traffic lights. Page 55

56.  This allows all turns to and
from the highway to be
made without crossing the
opposite direction of travel,
increasing the capacity
when compared to a
typical diamond
interchange.
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57. One set of
traffic signal
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58. Page 58

59. References:
 Highway engineering by
Clarkson H. Oglesby & R.
Gary Hicks
 Elements of roads and
highways by Max Fajardo
 www.highway
researchinterchangesInterch
ange (road) - Wikipedia, the
free encyclopedia.htm
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