To ensure correct and efficient auto routing calculations in maps, roads should be designed and created correctly in the proper hierarchy.
Garmin and GPS Mapedit has a number of road and highway polyline types that can be used for maps.
In most cases, GPS maps should mirror the actual situation in real life (ie use Major highway polyline type (0x01) for actual Major Highway), however for practical reasons, this may not always be possible.
The roads and highway polyline types in use currently in our maps are:
Residential Street (0x06)
Road (0x00) - DO NOT USE - Causes compilation to crash
REASON FOR DIFFERENT ROAD CLASSES
If a medium to large sized map with hundreds or thousands of roads were to beconstructed entirely based on a single road type (eg, Residential Street), an Auto Routingcalculation on the GPS unit may work but will take a very very long time
For efficiency of routing and speed wise, it’s better to add in higher order road classes.
This is actually how things work in reality
In real life, many residential streets (0x06) in suburbs will and should connect to a larger “main road” – this can be a Collector Road (0x05)
Collector Roads from different parts of the city will then divert traffic into a larger road (sometime it can be a dual carriageway or two one way streets either with or without a central median) called Arterial Road(0x04)
Arterial Roads in turn will in turn move traffic into either Other Highway (0x03), Principal Highway (0x02) or Major Highway (0x01) depending on the circumstances and location.
An analogy will be to think about a tree and how the main tree trunk (Major Highway) will move water (and nutrients) into
branches (Principal Highway) and then
into sub-branches (Arterial Roads/Collector Roads), then
into leaves (Residential Streets) and then
individual “veins” in the leaves (Alleyways/Unpaved roads)
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