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The standard equipment for
measuring traffic parameters in Sweden and Malmo is the “2 tube classifier” which
is used for temporary surveys. For permanent surveys the most common method is
magnetic loops in the road surface often used in a combined system for control
of traffic lights in crossings. Data from these permanent surveys are
transmitted via the optical fibre net that connects all the traffic lights in Malmö.
The equipment classifies the
vehicles in 13 different types from light passenger cars to heavy vehicles of
different types with or without trailers. Both the direction and speed of the
vehicles are also registered. The speed is divided into intervals, normally of
5 km/h.
The model Malmö
now uses for modelling and dispersion calculations is
the ENVIMAN. Normally only the number of vehicles in 3-4
vehicle categories are used: passenger cars, heavy trucks, diesel buses
and CNG buses. Sometimes also heavy trucks with trailers are used in the
calculation when it comes to peripheral roads.
The roads are divided into 13
different types ranging from motorway to local residential streets to specify
the emission factors. If the actual speed deviates from the
one in the chosen road type this can be taken into account. The timely
distribution of the traffic is taken into account in two ways, by specifying
the drive pattern throughout the day and the drive pattern over the year. The model also has an input for critical
traffic conditions/congestion. |