when traffic movement might be the most important consideration. There are generally no special pedes- trian crossing restrictions, but crosswalks may be provided where traffic volumes are high. To improve traffic flow, particularly at peak hours, it is sometimes desirable to provide collector roads with bus bays or turning lanes similar to those provided on arterial streets. Design speed Design speeds normally range from 50 km/h to 80 km/h. Ruining speed The normal running speed under free-flow conditions varies from 30 km/h and 70 km/h, with the higher values prevailing in suburban areas. Vehicle type in commercial and industrial areas, all types of vehi- cles including truck transports moving to and from arterials use urban collector roads. In residential areas, collectors carry a low percentage of trucks composed mainly of service vehicles. Connections Urban collector roads are connected to arterial and local roads, but connections to freeways are rarely found exceot in areas of concentrated development. A.5.7 Urban arterial roads Service function Urban arterial roads carry large volumes of all types of traffic moving at medium to high speeds. These roads serve the major traffic flows between the principie areas of traffic generation; and connect to rural ar- terials and collectors. In urban areas without free- ways, arterial roads provide the best quality of traffic service. The amount of direct access to adjacent development on urban arterial roads preferably should be limited. Desirably, such access should be confined to iocal and collector roads, by applying treatments such as frontage roads. Traffic volume Urban arterial roads normally experience traffic vol- umes of 5000 to 30 000 vehicles per day. Urban ar- terials may be divided or undivided. Flow characteristics The traffic flow is generally uninterrupted except at signalized intersections and crosswalks. Where sig- nals are closely spaced synchronization minimizes the interference to through movements. Parking and unloading are often prohibited where they might se- riously affect through movement of traffic, particularly at peak hour. Pedestrian crossing preferably should be limited to intersections or special crosswalks. Design speeu Design speed is in the range of 50 km/h to 100 km/h. Running speed Running speed under free flow conditions normally ranges from 40 km/h to 90 km/h, with the nigher val- ues prevailing in suburban areas. Vehicle type Urban arterial roads are usad by all types of traffic. Trucks may comprise as much as 20% of the total traffic volume. Both exprese and local buses are gen- erally routed on arterial roads. Connections Artarial roads connect to freeways, other arterials, and collector roads. In certain cases, lacal industrial or commercial roads connect to arterialg because of their location or the traffic volumes carried. It is un- desirable to nave local residential roads connect with arterials. A.5.8 Urban freeways Service functions Urban freeways accommodate high volumes of traftic moving at high speeds under free- flowing conditions. Urban freeways connect primary areas of traffic gen- eration and serve as urban extensions of principal rural hiqnways. They are intended to serve traffic be- tween large residential areas, industrial or commercial concentrations and the central business district. To provide optimum mobility for through traffic, service to adjacent lands is eliminated. No parking, unloading of goods, or pedestrian traffic is permitted. Traffic volumes Urban freeways normally carry traffic volumes in ex- cess of 20 000 vehicles per day. Fiow characteristics . To move high volumes at high speeds, urban freeways have uninterrupted flow conditions. This is provided by grade- separated crossings and interchanges. Par- king and pedestrians are prohibited. Urban freeways are generaily constructed on new alignments. Design speed The normal range of design speed is 100 km/h to 120 km/h. in special circumstances a design speed as low as 80 km/n is acceptable. Running speed The normal running speed under free-flow conditions varies between 70 km/h and 100 km/h. Vehicle type Urban freeways carry ail types of vehicles including a relatively high percentage of trucks, amounting up to 20% of the total volume. The only bus service on urbar freeways is express, with stops only at interchanges. Connections Urban freeways connect directly to intersecting or adjacent freeways and to most intersecting or adja- cent arterial streets. Some direct connections to col- lector streets may be provided in the central business district. A.6 SELECTION OF ROAD DESIGN CLASSIFICATION The design standards in this Manual are intended to be applied only after the classification of a road has been determined. The selection, is based on a knowi- edge of the purpose, function and general charac- teristics af the road and its relationship to other roads - in the network. For each road Clazsification given, there is a range. of dasign speeds and corresponding range of stan- dards. This allows variation in prevailing conditions to -be reflected in the geometric design by the selection of classification. Caretul application of standards for the 56 classifica- tions shown, bring the geometric features into. harmony.