KwaZulu-Natal Dept. of Transport is using g-tech for short term traffic counting
The volume and category of vehicles on the various sections of a road network is a key factor in network planning, determining levels of service, public transport planning and for pavement design. Traffic volumes are usually determined by using a combination of permanent continuous counts and short duration counts.
Continuous counts are carried out using counting loops with sophisticated equipment housed in permanent stations at key locations within the road network. They help road agencies understand time- of-day, day-of-week and seasonal variations in traffic volumes. Because continuous counts are expensive, most road agencies would have a few permanent stations but use short term duration counts as the main method of determining traffic volumes.
There are many methods that can be used to carry out short duration counts. The methods can be broadly classified as electronic or manual. Because of the need to classify traffic for public transport planning, the Department of Transport uses manual traffic counting as the predominant method of carrying out short duration counts.
Challenges in manual counting
The department faces a number of challenges when using external service providers to carry out manual traffic counting.Most notable challenges include enumerators counting wrong intersections; enumerators allocating counts to the wrong intersection legs even if they are at the correct intersection; enumerators arriving at intersections before/after time and guessing counts for missing periods.
Dealing with challenges
Over the years, the department experimented with various measures to limit the magnitude of errors arising from the above practices, with limited success. This situation persisted until the department started monitoring the enumerators using an internet-based tracking system. Monitoring involves assigning a GPSenabled mobile phone to each enumerator. The mobile phones have software installed to send GPS location signals to a central tracking server. The counting supervisors can monitor each enumerator to ensure they are at the correct intersection and are counting the correct intersection leg. If for any reason any enumerator arrives late or leaves early, the exact time of arrival or departure is known. This ensures data integrity since guessed counts can be removed from the captured data. Using mobile phones presents an added advantage since the counting supervisor can guide lost enumerators to the correct intersections.
Manual counting presents a cheaper and viable alternative for carrying out short term traffic counting. In cases where differentiation is required between passenger minibuses and cars, and between buses and trucks, it could be the only alternative. The use of GIS technology by the Department of Transport has ensured that manual counts can be done with a reasonable level of accuracy.
