Importance of Road Shoulder & Drainage

Importance for Paved Shoulders

Safety - roads with paved shoulders have lower accident rates, as paved shoulders:

  • Provide space to make evasive maneuvers;
  • Accommodate driver error;
  • Add a recovery area to regain control of a vehicle, as well as lateral clearance to roadside objects such as guardrail, signs and poles;
  • Provide space for disabled vehicles to stop or drive slowly;
  • Provide increased sight distance for through vehicles and for vehicles entering the roadway (rural: in cut sections or brushy areas; urban: in areas with many sight obstructions);
  • Contribute to driving ease and reduced driver strain;
  • Reduce passing conflicts between motor vehicles and bicyclists and pedestrians;
  • Make the crossing pedestrian more visible to motorists; and
  • Provide for storm water discharge farther from the travel lanes, reducing hydroplaning, splash and spray to following vehicles, pedestrians and bicyclists.

Capacity roads with paved shoulders can carry more traffic, as paved shoulders:

  • Provide more intersection and safe stopping sight distance;
  • Allow for easier exiting from travel lanes to side streets and roads (also a safety benefit);
  • Provide greater effective turning radius for trucks;
  • Provide space for offtracking of truck's rear wheels in curved sections;
  • Provide space for disabled vehicles, mail delivery and bus stops; and
  • Provide space for bicyclists to ride at their own pace;

Maintenance roads with paved shoulders are easier to maintain, as paved shoulders:

  • Provide structural support to the pavement;
  • Discharge water further from the travel lanes, reducing the undermining of the base and subgrade;
  • Provide space for maintenance operations and snow storage;
  • Provide space for portable maintenance signs;
  • Facilitate painting of fog lines.

Importance of Drainage

The presence of water in a highway layer reduces the bearing capacity of the road, and in doing so it also reduces the structure's lifetime. Indeed, the recent extremely cold winter in many parts of Europe has shown that in colder climates there is a risk of frost damage when water is present resulting in costly potholes, so drainage systems performing properly are important in road design.

And while motorists driving along a road see little of such systems, they are an expensive and vital element of the structure where the surface drainage system looks after the run-off water from rainfall. This is where the waterproof surface with a crossfall leads the rainwater to drains. Sub-surface drainage systems safely remove groundwater and water getting in through the pavement's surface.

Case Studies in Kenya

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