How are Posted (Real) Road Speed overspeed events generated

What is Real Road Speed?

In order to accurately report overspeed and monitor driver behaviour, Smartrak needs to calculate and report Real Road Speed.

Real Road Speed provides the ability to understand when and where drivers are speeding in relation to the road speed of the actual road they are travelling on and not just 100 km/hr roads.  It ensures more accurate reporting of driver behaviour and under / overspeed events.

How do we calculate Real Road Speed?

1. The tracking application detects a trip has started. (key on)

2. Every 20 seconds a location/timer event will be generated. This event contains information like:

   1. Location

   2. Speed

   3. Time

3. The system will perform a real road speed check

   1. If this event is above (or equal to) the posted speed limit + threshold (defaults to 5):

      1. Create overspeed event.

   2. If this event is below the posted speed limit + threshold and the previous event was an overspeed event:

      1. Create below speed event.

Limitations

Event Frequency

Each timer event is generated at a 20-second frequency. This frequency has an impact on a few things:

An overspeed period reports on:

• Start time

• End time

• Distance

• Min speed

• Max speed

Due to the fact that we are using events at 20-second intervals, an overspeed period can inaccurately be reporting an overspeed state for up to 18 seconds.  Periods will only ever be a maximum of 20 seconds inaccurate.

Missing overspeed events

Since we are only taking a snapshot of the speed every 20 seconds the is the possibility of missing an overspeed period entirely if it falls within the 20 seconds between pings.

Speed Validation / GPS Bounce

Every overspeed event undergoes the following speed validation (any events which do not pass all these checks are automatically invalidated):

• Satellite Quality - GPS position from a minimum of 4 satellites to ensure accuracy.

• Changes in speed - Checks GPS speed hasn't increased or decreased by more than 20km/h in the last second.

• Point to Point Speed - GPS speed is within +/- 9km/h of the calculated point-to-point speed, given the previous and current position.

NOTE: Despite all this validation, there is still the possibility for false-positives due to GPS bounce. Please ensure you check for false-positives as detailed later in this document.

Checking for False Positives

Due to the nature of GPS it is important to understand that speeds reported can be inaccurate on occasion. If the GPS satellite coverage is low or the vehicle is in conditions that can affect the signal, the speed can be miscalculated. Taking this into account we advise that people watch for trends in speeding patterns rather than singling out a specific event.

When singling out specific events, please consider the following to ensure their validity and that they aren't false-positives:

• Is the overspeed event on the road?
  If the event is half-way up a hill or on top of a house, then the event was subject to GPS bounce and is not correct.

• Is the overspeed event in a highly built-up area?
  Even if the event is on the road, sometimes a highly built up area will create GPS bounce off tall buildings, trees, canyons and gullies.

• Check the events immediately before and after the overspeed event
  If there is a large jump in speed in a small amount of time, this event may not be correct.

• Does the vehicle have a pattern of overspeeding or high g-force events compared to other vehicles
  Further investigation of vehicle history may be appropriate to ensure the unit is providing accurate data.

Again, Smartrak recommends that overspeed events are viewed as a trend for a driver, rather than individual events. Exceptions to this may include situations where a driver has dangerously exceeded acceptable limits.

If there is a pattern of overspending or high g-force events for individual drivers, further investigation may be appropriate.