CE562 Lecture 12 Cross Section Elements 3

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CE562 Lecture 12 Cross Section Elements (3)

• Text A Policy on Geometric Design, pp. 305-375

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Noise Control

• General consideration
• Noise is an unwanted sound. A highway designer
  should evaluate the probable noise level and
  consider means to reduce the noise if needed.
• The unit of noise is decibel (dB). Increase in
  noise by 10 dB makes impression of doubling the
  noise. A doubling in the sound intensity
  (acoustic energy) increases the noise by 3 dB.
  Noise decreases by 3-4.5 dB with doubling of
  distance from a highway.
• General Design Procedure
• 1. Define noise-sensitive areas along highway,
• 2. Determine criteria for noise impact,
• 3. Measure current noise level (prior highway
  construction),
• 4. Predict the noise level expected after highway
  is constructed,
• 5. Evaluate the noise impact,
• 6. Design countermeasures if needed.

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Noise Control

• Predicting noise level
• The noise level should be predicted for the worst
  traffic hour for a typical day. The following
  factors should be considered
• traffic characteristics (speed, volume, and
  compositions)
• topography (vegetation, barriers, distance)
• roadway characteristics (configuration, pavement
  type, grades, type of facility)
• Design countermeasures
• highway relocation
• depressed highway sections
• earth berms
• noise barriers (concrete, wood, metal, masonry
  walls)
• shrubs and trees

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Noise ControlDepressed Highways
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Noise ControlElevated Highways
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Roadside Control (Access Control)

• Roadside inference (vehicle movements to and from
  businesses, residences, and other developments)
  affects the efficiency and safety of a highway.
  Roadside control pertains to location, design,
  and operation of access driveways, and other
  roadside elements.
• Means of driveways control
• driveways with permitted right turns only
• permission for all new driveways
• driveway spacing and layout
• grouping of driveways
• frontage roads
• Special rules address mailboxes location.

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Roadside Control
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Roadside Control
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Roadside Control
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Roadside Control
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Roadside Control
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Roadside Control Safety Consideration (Indiana)
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TunnelsGeneral Considerations and Types

• The following conditions may warrant tunnel
  construction
• long, narrow terrain ridges
• larger and complex intersections or sequence of
  major intersections on an irregular or diagonal
  street pattern
• railroad yards, airports and runways, or similar
  facilities
• parks or other land uses
• costly right-of-way acquisition
• Types of tunnels
• constructed by mining methods (horse-shoe or
  circular)
• constructed by cut-and-cover methods
  (rectangular)
• or
• hard-rock tunneling
• soft-ground tunneling

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TunnelsDesign Considerations

• Tunnels create discomfort (feeling of confinement
  and traffic noise) and are expensive. Tunnels
  should be
• as short as possible
• designed on tangents if possible
• graded with consideration of drivers comfort and
  construction cost
• ventilated and lighted
• The standards for alignment on open sections
  apply to tunnels with exception that the minimum
  requirements should be considered to minimize
  costs.

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Minimum design
Exhibit 4-17
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Exhibit 4-18
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Ted Williams Tunnel BostonBIG DIG

• The Ted Williams Tunnel will be carrying more
  than 90,000 vehicles a day.

Planned cost 2.5 billion, by now -- 14 billion
(entire project)
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TUNNELS MODEL
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CUT-AND-COVER
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CUT-AND-COVER FINISH WORK
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TUNNEL RAMP UNDER CONSTRUCTION
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TUNNEL RAMP OPENED
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Pedestrian Crossings and Ramps

• Pedestrian overcrossings and underscrossings are
  warranted when
• peak pedestrian volume is heavy and vehicular
  traffic is moderate or heavy (CBDs, factories,
  schools), or
• abnormal hazard or inconvenience for pedestrians
  takes place (cross streets terminated by freeways
  or expressways).
• Design rules
• Overpassings should be consider before
  underpassings is considered (less expensive,
  preferable by pedestrians),
• Fences near pedestrian separations prevent
  at-grade highway crossing,
• All pedestrian separations should have ramps
  stairways can be provided in addition,
• Minimum width of walkways is 2.4 m,
• Screens are recommended on overpassings where
  dropping objects on the traveled way is the
  concern (near schools, playgrounds, not
  frequently patrolled by police),
• Continuous vision through the underpass reduces
  pedestrians discomfort.

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Exhibit 4-22
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Bus Turnouts

• Bus turnouts remove the bus from the traffic
  lanes.
• Freeways
• Bus turnout includes
• deceleration section
• standing section
• acceleration section
• separation between bus lane and through lanes
• passenger platform
• pedestrian separation (overpass, ramps, stairs)
• signs and markings
• Arterials
• Bus turnouts should be considered where possible.
  They include
• deceleration lane or taper (minimum 51)
• loading area (3-3.6 m wide and 15 m long for each
  bus)
• merging (reentry) taper (minimum 31)

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Park and Ride

• Park-and-ride facilities offer convenient
  transfer from the passenger car (or bicycle) to
  public transit vehicles (bus, city train,
  underground).
• Location
• Adjacent to the street or highway
• Visible to the commuters
• Preceding the bottleneck
• Close to the residential area
• Design
• Elements of park-and-ride facility
• long-term parking lot
• short-term parking lot
• bicycle parking
• passenger pickup and dropoff
• passenger shelters
• bus (train) loading and unloading areas
• taxi service
• bus roadways
• lighting and drainage

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On-Street ParkingUse

• Curb-parking should be prohibited on freeways and
  major arterials
• Recommended on minor arterials, collectors and
  local roads located in developed areas
• Parallel parking preferred over angle parking
  (performance of through lanes and safety)

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On-Street ParkingDesign Rules

• Arterials
• Minimum width of parking lane is 2.4 m
  (recommended width is 3.0-3.6),
• Minimum width of parking lane with adjacent
  bicycle route is 3.0-3.6 m.
• Urban collectors
• Minimum width of parking lane is 2.4 m
  (recommended width is 3.0-3.6),
• Minimum width of parking lane with adjacent
  bicycle route is 3.0-3.6 m,
• In residential areas, 10.8 m two-lane two-way
  traveled ways are sufficient (2.1 m parking lanes
  and 3.3 m through lanes).
• Local streets
• In residential areas 7.8 m traveled ways are
  sufficient for two-way traffic.
• Parking lanes should end 6.0 m in advance of the
  intersections.

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Exhibit 4-31