Arterial roads — Making the connection

The urban principal arterial system serve the major centres of activity of urbanized areas, the highest traffic volume corridors, and the longest trip desires. This system carries most of the trips entering and leaving the urban area, as well as most of the through movements bypassing the central area. In addition, significant intra-area travel, such as between central business districts and outlying residential areas, between major inner-city communities, and between major suburban centres, is served by this class of facility. In urbanised areas, this system provides community for all rural arterials that intercept the urban boundary.

The urban minor arterial street system interconnects with and augments the urban principal arterial system. It accommodates trips of moderate length at a somewhat lower level of travel mobility than principal arterials do. This system distributes travel to geographic areas smaller than those identified with the higher system. This system places more emphasis on land access than the higher system does and offers lower traffic mobility.

The urban collector street system provides both land access service and traffic circulation within residential neighbourhoods and commercial and industrial areas. It differs from the urban arterial system in that facilities on the collector system may penetrate residential neighbourhoods, distributing trips from the arterials through the area to their ultimate destinations. Conversely, the urban collector street also collects traffic from local streets in residential neighbourhoods and channels it into the arterial system. In the central business district, and in other areas of similar development and traffic density, the urban collector system may include the entire street grid.

The urban local street comprises all facilities not in one of the higher systems. It primarily permits direct access to abutting lands and connections to the higher order systems. It offers the lowest level of mobility and usually contains transit routes. Service to though-traffic movement usually is deliberately discouraged.

Arterial Roads are the main transport routes within the road hierarchy. The main elements to consider when planning arterial roads include:

• No frontage access;

• Development set well back from the highway;

• All access to premises provided via collectors;

• Number of intersections to be minimised;

• Suitable at-grade channelised intersections for minor flows;

• Pedestrian and slow-moving vehicles clearly segregated wherever possible;

• Parking on the road should not be permitted or necessary;

• Where necessary, parking/stopping to be provided clear of main carriageway(s);

• Bus stops and other loading areas (only permitted in exceptional circumstances) should be in separate well designed laybys;

• Grade separated intersections for extremely high flows (when there is no at-grade intersection these are known as freeways; when there are limited at-grade intersections these are called expressways); and,

• Suitable for all heavy goods vehicle (HGV) movements especially through-trips.

Collector Roads form the next level below arterial roads in a road hierarchy. The needs of moving traffic still predominate but they also contribute to access requirements. They serve to feed traffic onto and off the main road network at the beginning and end of journeys. The main elements to consider when planning collectors include:

• Frontage access may be allowed but individual vehicle accesses should be avoided from adjacent buildings, except where large traffic generators exist;

• These roads will be within or close to residential areas and motorists need to be aware of pedestrians, especially young children; adjacent areas alongside such roads can become play areas unless careful consideration is given to ensure that open areas between routes do not develop in that way;

• The road is only for local traffic; through-traffic is more adequately accommodated on an alternative, more direct road;

• Where possible, an industrial traffic route should not pass through a residential area;

• Vehicle speeds should be kept low, so long straight roads should be avoided;

• Parking may be allowed, but alternative off-road provision should be made if possible;

• Non-motorised traffic is of equal importance to motor traffic and separate routes should be provided if possible;

• Dependent upon the traffic flows the road width can be varied to provide for parking or to give emphasis to crossing points;

• Bus stops can be located on the carriageway but should be near well-defined crossings;

• Through-movements should be made awkward and inconvenient to discourage them; and,

• Minimum HGV through-trips.

Local Roads are for access only. The main elements to consider when planning locals include:

• Vehicle flows to be kept to a minimum;

• All unnecessary traffic eliminated;

• Vehicle speeds to be kept low by careful and deliberate inclusion of obstructions to create meandering alignments;

• Access roads kept short where possible;

• Cul-de-sac and loop roads to be used wherever possible to deter through-traffic;

• Intersections to be three rather than four leg and kept compact to aid pedestrian movement;

• Pedestrians and vehicles can share space;

• Carriageway width can be reduced to emphasise pedestrian priority;

• Entrance/exit points of access should be clearly identified by threshold treatments, e.g. changes in geometric layout, landscaping, building or even gateways and signing;

• Parking and stopping within the street is permitted although, adequate provision should be provided within individual properties or separate garage areas; and,

• HGV activity: only related-activity permitted in residential areas; delivery of goods and services permitted in other areas.

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