The main functions of rural mobility and access/activity roads are as follows:
a) The main function of rural mobility roads is to connect areas that are large traffic or strategically important generators. These generators typically include cities, towns, villages, rural settlements, border posts, mining areas, seaports, airports, large game and nature parks, other mobility roads, etc.
b) The main function of rural access/activity roads is to provide access to individual properties, whether farms, settlements, mines, tourist areas, game and nature parks, heritage sites, etc. Animals and farm equipment should not be allowed on
mobility roads but can be accommodated on access/activity roads provided that appropriate measures are introduced to manage their impact.
Criteria for differentiating between the different classes of rural roads are a) size or importance of the trip generator, b) reach of connectivity and c) the travel stage. Some indication is also given of typical traffic volumes but this should not be used in establishing the class of road.
The provided criteria rely primarily on qualitative rather than quantitative terms. It is not possible to provide exact quantitative criteria (such as traffic volumes generated, trip length or vehicle-kilometres of travel) to distinguish between classes. However, it is possible to provide some broad guidance on the percentages of the total of different classes of roads in rural areas. These percentages are as follows (FHWA, 1989):
Rural road Class FHWA description Percent of veh-km Percentage of road length
R1, R2 Principal arterials 30 – 55% 2 – 4%
R1, R2, R3 Principal plus minor arterials 45 – 75% 6 – 12%
R4 Collectors 20 – 35% 20 – 25%
R5 Local roads 5 – 20% 65 – 75%
The Rural Road Functional Classification is summarized in Table B at the back of this Manual and is described in the following sections.
4.4.2. Class R1 rural principal arterials
Rural principal arterials carry countrywide traffic between:
• Metropolitan areas and large cities (population typically greater than about 500 000);
• Large border posts;
• Other Class 1 Arterials; and
• Smaller centres than the above when travel distances are very long (i.e. longer than 500 km).
R1 arterials should only be used to carry through traffic and alternatives for local traffic should be provided.
Travel distances on R1 arterials are seldom less than 50 km in length. Some routes, however, can carry traffic over long distances and can even reach from one side of the country to the other,
The routes are typically characterised by higher through traffic volumes. Average annual daily traffic (AADT) would in most cases exceed 1 000 vehicles per day on the long distance routes, 5 000 veh/day on the medium distance routes and can reach 100 000 veh/day or more on shorter routes.
Class R1 arterials should preferably be continuous routes that would typically serve several nodes along each route. The nodes do not have to be located on the route; in fact the route should preferably bypass the nodes, but should be located within a reasonable distance from the routes.
4.4.3. Class R2 rural major arterials
Rural major arterials carry inter-regional traffic between:
• Smaller cities and medium to large towns (population typically greater than about 25 000);
• Smaller border posts;
• Class 1 and other Class 2 routes;
• Important regions, transport nodes and commercial areas that generate large volumes of freight and other traffic such as seaports and international airports.
• Smaller centres than the above when travel distances are relatively long (longer than 200 km).
R2 arterials should only be used to carry through traffic and alternatives for local traffic should be provided.
Travel distances on R2 arterials are seldom less than 25 km in length. Some routes, however, can carry traffic over long distances and can reach from one side of a province to the other or even into adjoining provinces.
AADT would typically exceed about 500 vehicles per day on the long distance routes, 2 000 veh/day on medium distance routes but on shorter routes the volumes could exceed 25 000 veh/day.
Class R2 arterials should preferably be continuous routes that would usually serve several nodes (typically in a province). The nodes do not have to be located on the route, but should be located within a reasonable distance from the routes.
4.4.4. Class R3 rural minor arterials
Rural minor arterials carry inter-district traffic between:
• Small towns, villages and larger rural settlements (population typically less than about 25 000);
• Smaller commercial areas and transport nodes of local importance that generate relatively high volumes of freight and other traffic in the district (public transport and freight terminals, railway sidings, small seaports and landing strips);
• Very small or minor border posts; • Tourist destinations;
• Other Class 1, 2 and 3 routes.
• Smaller centres than the above when travel distances are relatively long (longer than 50 to 100 km).
The typical length of these routes would vary between about 10 km and 100 km. These roads are not busy and traffic volumes between 100 and 2 000 per day are typical.
Class R3 arterials are not always continuous, often stopping when a particular destination is reached, although they could also serve more than one node in a district and can cross into adjoining districts.
4.4.5. Class R4 rural collector roads
These roads form the link to local destinations. They do not carry through traffic but only traffic with an origin or destination along or near the road. A collector road must never be quicker to use to pass through an area than the alternative mobility road.
These roads would typically give access to smaller rural settlements, tourist areas, mines, game and nature parks and heritage sites. The roads can also provide direct access to large farms. Collector roads can also be provided within larger rural settlements to provide a collector function in such settlements.
The length of these roads would mostly be shorter than 10 km. Traffic volumes should not be more than about 1 000 vehicles per day.
4.4.6. Class R5 rural local roads
Class 5 roads provide direct access to smaller individual properties such as within rural settlements, as well as small to medium sized farms in rural areas. They serve no other purpose than to give such access.
The length of these roads would mostly be shorter than 5 km. Traffic volumes should not be more than about 500 vehicles per day.
4.4.7. Class R6 rural walkways
These paths provide essential pedestrian and non-motorized traffic access to the road network. They are typically informal, rarely constructed and are generally the result of frequent use.