The load from traffic of the road pavement is believed to be a major cause of road degradation. Current regulations for allowed load refer to the static load only, not the actual dynamic load. The two differs due to road unevenness, where its geometrical shape is a major component, besides its magnitude. Since vehicles are dynamic objects they have a fairly complex response to road shape. That means the load needs to be calculated according to the respective differential equations of each vehicle. Further, the ratio between the length of roads and response length of vehicles can be extremely large requiring highly efficient analysis methods, such as digital filters.

Below, the dynamic load in the tires and suspension of a simple heavy vehicle (truck) is calculated with a digital filter having 7 degrees of freedom (four wheels, body translation, pitch and roll). The load in the tires is identical to the load on the road. The unevenness is here an asymmetric (to display ‘roll’) wash board of large magnitude, resulting in up to 100% excess load (twice the static): With the conventional exponent four model of road fatigue stress, the life span for 100% excess dynamic load is reduced no less that 16 times.
By analyzing existing roads with digital filtering of scanned road surfaces in this way, pavement loads are resolved along the road. Presumably, as the road wears down end its unevenness increase dynamic loads also increase. Since that may accelerate the road degradation and thus limit its life span, this information is valuable for optimal road maintenance. The analysis could be repeated every year or so, with (in the context of road maintenance) negligible cost.

This is one of several applications of our general RoadNotes® concept. Another (featured image) is analysis of whole-body vibrations for bus-drivers. Its goal is to evaluate the working environment (especially spinal cord injury, according to ISO 2631-5) with respect to long exposure of vibrations – complaints from bus drivers of pain in the back is ubiquitous.

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