King Fahad University of Petroleum

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King Fahad University of Petroleum Minerals

• CE-576-Geometric Highway Design
• Urban Arterials

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Chapter VII
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Objective (Urban Arterials)

• General Design Considerations
• Access Management
• Pedestrian Facilities
• Provision for Utilities

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• Operational Control Regulations
• Frontage Roads
• Grade Separations Interghanges
• Erosion Control
• Lighting

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General Design Considerations
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Design Speed

• Generally range from 50 to 100 km/h 30 to
  60mph.

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• Design Traffic Volume
• The design year is normally 20 years.
• DHV is the most reliable traffic volume measure
  representing the traffic demand.
• Capacity analysis is also used as a design tool.

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Level of Service

• For acceptable degree of congestion, rural
  suburban arterials their auxiliary facilities
  should be designed for level of service C.
• In heavily developed areas use level of service D
  with using one-way streets or alternative bypass
  routs to improve the level of service.

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Sight Distance

• The following table shows the min. sight distance
  for arterials

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Alignment

• The alignment should be developed according to
  the design speed for principal arterials to be
  constructed on new location not restricted by
  right-of-way construtions.

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• Grades
• Flat grades are desirable, with providing min.
  gradients for longitudinal drainage in curbed
  sections.
• In case of steep grades cannot be flattened,
  climbing lanes should be considered.

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• The following table shows the recommended max.
  grades for urban arterials

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• Superelevation
• Curves on low-speed, curbed arterial streets are
  often not superelevated.
• Cross slopes
• Cross slopes ranges from 1.5 (drainage flow
  across single lane) to 3 (drainage flow across
  several lanes).

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• Vertical Clearance
• Vertical clearance should be 4.9m over the entire
  roadway width.
• In highly urbanized area, min. clearance 4.3m is
  allowed if there is alternative rout with 4.9m
  clerance.

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• Lane Width
• Lane widths vary from 3.0m to 3.6m 10 to 12ft,
  width of 3.3m is widely used.
• Under interrupted-flow conditions at low speeds
  (70 km/h 45 mph or less), narrower lane widths
  are used.

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• Curbs Shoulders
• The outside edges of shoulders are often curbed
  closed drainage system provided to minimize the
  amount of right-of-way needed.
• Number of Lanes
• Normal range is 4 to 8 lanes in both directions.

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Medians

• On lower volume arterials often no median used,
  or median of width 1.2m 4ft.
• At intersections median width at least 3.6m
  12ft to accommodate left-turn movements.
• For 3.6m 12ft turning lane, median width at
  least 5.4m 18ft with 1.8m 6ft medial
  separator between turning lane opposing traffic
  lane.

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• At restricted locations 3.0m 10ft with 0.6m
  2ft medial separator.
• Raised curbed median used on low-speed urban
  arterials it is not desirable on high-speed
  arterials unless a median barrier is provided.
• Flush median can be used if it is improved by
  contrasting pavement texture by improved
  delination.

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Medians

• Median width at unsignalized intersections at
  urban suburban areas is less than 7.5m 25ft,
  widths from 9 to 15m 3 to 5ft have higher crash
  rates but they operate well.

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• At urban suburban signalized intersections the
  efficiency of signal operations decreases as the
  median width increases. Widths more than 18m
  60ft are undesirable.

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• Drainage
• Full width of shoulder or parking lane is
  utilized to conduct surface water to the drainage
  inlets. If no shoulder or parking lane one half
  of the outside lane is utilized.

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• Parking Lanes
• Parking lane width for P should be 3.0m to 3.6m
  10 to 12ft.
• If parking lane is not used as through lane,
  width of 2.4m 8ft is enough.
• Parking lane can be used as through traffic lane
  and as storage lane for turning vehicles.

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• The following figure shows parking turnout at
  downtown district.

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Borders Sidewalks

• Min. border width is 2.4m 8ft. 3.6m 12ft or
  more is more desirable.
• The following figure shows arterial street in
  residential area.

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• Railroad-Highway Crossings
• Frequent crossings or during high-volume traffic
  periods should treated by grade separation.
• Infrequent crossings or during off-peak periods
  can be at grade with traffic control.

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• Horizontal Clearance to Obstructions
• In curbed streets a clearance between curb face
  object is 0.5m 1.5ft or wider.
• 1.0m 3ft clearance to roadside objects provided
  near turning radii at intersection driveway

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Access Management

• Access control by statute.
• Access control by zoning.
• Access control trough driveway regulations.
• Access control through geometric design

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• Access Control by Statute
• Access is usually limited to the cross streets or
  to other major traffic generators.
• Access Control Through Driveway Regulations
• Permits of driveways entrances can be
  controlled to minimize interference with the free
  flow of traffic on the arterial.

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Access control by Zoning

• Property uses can be limited to those that
  attract very few people excluding uses that
  generate significant volumes of traffic during
  peak hours.
• Zoning regulations should require ample
  off-street for building permit approval.

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• Internal arrangement of the land-use development
  should be such that parking spaces more distant
  from arterial are most attractive to the user.
• Zoning ordinances should require a suitable
  connection to the arterial street or to cross
  street for a major traffic generator.

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Access Control Through Geometric Design

• Left turns can be accommodated by U-turns at
  intersections, jug-handle configurations, or
  around-the-block movements.
• Right-turn-in right-turn-out arrangements are
  another important design feature to control
  access to an arterial.
• Frontage roads grade separations provide the
  ultimate in access control.

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• Pedestrian Facilities
• On lower classes of arterials, pedestrian
  facilities usually limited to crosswalk markings.
• On higher-volume arterials grade separations for
  pedestrians are sometimes used, crosswalks are
  used more.
• Pedestrian walk signal is desirable on wide
  arterials with frontage road.

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• At channelized intersections or if there is a
  median, curbs should be used for areas to be used
  by pedestrian for refuge during the crossing.
• Provision for Utilities
• Desirably utilities are located underground or at
  the outer edge of the right-of-way.

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Operational Control and Regulations

• Traffic control devices.
• Regulatory measures.
• Directional lane usage.

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Traffic Control Devices

• Signal spacing is achieved by controlling
  intersection locations during early development
  stage.
• If this cannot be achieved, suitable time-space
  diagrams based on traffic forecasts may be used.
• Signal system should be flexible to control
  traffic demands from hour to hour from day to
  day.
• Signal system should allocate green time to each
  movement based on the demand of that movement.

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• Where multiple phasing is needed to control
  movements at intersections, the detection the
  programming equipment should provide capability
  to skip specific signal phases where there is no
  traffic demand.
• Idle lost green time due to lack of demand or
  too many phases should be kept min.
• Proper marking is important to enhance operation
  of an urban arterials. And adequate crosswalk
  markings enhance pedestrian safety.

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Regulatory Measures

• Restrictions on turning movements (right left
  turns).
• Prohibition of curbside parking, stopping, or
  standing.

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Operational Control for Right-Turn Movements

• At intersections, heavy pedestrian movement
  short corner curb radii slowing delaying the
  turning vehicles, then turning vehicles will
  delay through traffic.
• In such cases, it is desirable to prohibit turns
  during certain hours if there are alternative
  routs.

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Operational Control for Left-Turn Movements

• Left-turn demands should be accommodated as near
  as practical to the desired turning point.
• If desired turning point cannot be achieved, move
  those left turns to more suitable locations but
  not more than two blocks from the desired turning
  point.
• Where left-turns are permitted from arterial
  street provide left-turn storage lanes at
  intersection unless it is impractical to provide
  them.

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Regulation of Curb Parking

• At higher speeds during periods of heavy
  traffic movement, curb parking should not be
  permitted.
• The distance from corner of the intersection to
  the nearest parking stall is at least 6.0m 20ft
  from a crosswalk.

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Directional Lane Usage

• One-way operation
• Reverse-flow operation

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One-way Operation

• One-way operation can be employed if
• A single two-way street does not have adequate
  capacity, particularly where left-turn movements
  are difficult to handle.
• There are two parallel arterial streets a block
  or two apart.
• There are sufficient number of cross streets
  appropriate spacing to permit circulation of
  traffic.

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• The choice of one or two-way operation depends on
  which type can serve the traffic demands most
  economically with greatest benefits to the
  adjacent property.

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Reverse-flow Operation

• On 5-lane street, 3lanes can be operated in the
  direction of heavier flow.
• On 6-lane street with directional distribution 65
  to 35 , 4 lanes can be operated inbound 2
  outbound at morning peak vice versa at evening
  peak.
• 3 or 4-lane streets can be operated with reverse
  flow by operating one lane in the direction of
  lighter flow.

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• Reverse flow can be applied on divided facilities
  (termed contra flow operation) with more
  difficulty than undivided facility

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Frontage Roads Outer Separations

• Providing sufficient distance for turn-lane
  storage on the cross street is an important
  design feature of frontage road.

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Grade Separation Interchanges

• Locations where grade separation should be
  considered on urban arterials streets are
• At very high-volume intersections between
  principal arterials.
• At high-volume intersections having more than 4
  legs.

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• At high-type arterial intersections where all
  other intersections are grade separated.
• At all railroad crossings.
• Where terrain conditions favor separation of
  grades.

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• Erosion Control
• Seeding, mulching, sodding, and landscaping are
  usually used to control erosion.
• Lighting
• Lighting is important to improve operation and to
  prevent crime.
• Lighting should be continuous if not practical
  to be continuous at least to be provided at
  locations such as intersections ramp termni.

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Thank You