Cross sectional profile

• Traffic Lanes
  • A traffic lane is a designated roadway section for one-way vehicle flow. Its number and width significantly affect safety, capacity, driving comfort, and operating speed.
  • Australian and New Zealand roads typically use standard traffic lane widths of 3.5 m, allowing large vehicles to pass safely without lateral movement. Wider lanes (up to 3.7 m) are recommended for multi-combination trailers, and even larger lanes may be required for special vehicles like mobile cranes. Lane widening on curves accommodates truck tracking but should avoid exceeding 4.6 m to prevent dual car use. Narrower lanes (down to 3.3 m) can be used in low-speed, low-truck, or constrained areas with satisfactory safety records.
• Road Crossfall
  • Crossfall is the slope of a carriageway designed for drainage and superelevation, requiring at least 2.5-3% to prevent water retention, potholes, and pavement deterioration.

• Crown Lines
  • On straight two-lane roads, centrally placed crowns with up to 6% grade change and 2m rounding ensure water drainage and vehicle stability, minimizing destabilizing forces on trucks
     

• Shoulders

  • Road shoulders provide structural support to pavement layers and serve traffic functions such as recovery space for errant vehicles, refuge for stopped vehicles, emergency use, and cyclist space. Their width, influenced by traffic and environmental factors, enhances safety and driver comfort while reducing maintenance costs and crash rates, especially when sealed (0.5–1.5 m width is optimal). Shoulders generally have a steeper crossfall than traffic lanes for drainage, except when sealed with full-depth pavement. On superelevated sections, shoulder crossfalls should match traffic lanes to maintain consistency

 

 

• Verge

  • In Australia, the verge connects the shoulder to the batter, while in New Zealand, it extends from the shoulder hinge to the legal road boundary. This guide defines the verge as the area between the shoulder and the batter. Verges provide a safe transition for errant vehicles, support for road edges, space for infrastructure and utilities, and help reduce stormwater scouring. Terminology may vary, especially in urban areas where local councils define the verge differently, often as the area between the kerb and road reserve boundary.

     

• Batters
  • Batters are sloped surfaces connecting road elements to the natural surface, serving as recovery areas, landscaped zones, or maintenance paths. They include cut/fill batters, table drain batters, and median batters, with slopes expressed in horizontal-to-vertical ratios (e.g., 6:1). Batter design considers stability, safety (e.g., 4:1 slopes are recoverable for cars, 10:1 for trucks), maintenance, environmental impact, and aesthetics. Flatter slopes improve safety and erosion control, while steeper slopes may require barriers as per Austroads guidelines.

• Roadside Drainage
   

  Roadside open drains are used alongside unkerbed roads to collect and direct runoff from road pavements, culverts, and adjacent areas, ensuring traffic safety and pavement strength. Their functions include intercepting runoff from catchments, collecting water from road formations and slopes, and safely disposing of it. Effective design balances hydraulic efficiency with safety, construction economy, low maintenance, and environmental considerations, often reducing a drain's capacity to meet these requirements. Common types include table drains, catch drains, median drains, and kerb-and-channel systems.

   

• Table Drains
  Table drains, located outside shoulders in cuttings or alongside raised carriageways, are designed to drain pavements effectively by positioning their invert level below the pavement subgrade, typically by 300 mm. Protection against scour, such as grassing, rock lining, or concrete, may be necessary for steep or erosion-prone areas. Flat-bottom table drains are preferred over "V" drains as they reduce scouring, improve safety for vehicles, and enhance sightlines. Proper slope (-0.5% to -1.5%) ensures water flows away from the carriageway, though in flat areas, water retention may damage the pavement.

 

• Catch Drains
  Catch drains are positioned on the high side of cuttings, typically at least 2 m from the batter's edge, to intercept surface and seepage water, preventing batter face scour and table drain overloading. In some cases, catch banks are used as alternatives to manage seepage and enhance batter slope stability.

 

• Kerb and Channel
  Kerb and channel systems collect and convey surface water to discharge points, delineate carriageway edges, separate traffic from pedestrians and other uses, and support pavement edges. They can also substitute underground drainage systems for table drains, reducing the width of cut and integrating drainage more efficiently in urban areas.