Save the robots

| Tuesday November 24, 2009 00:00

It must be costing inordinate amounts of money to implement this regressive, inefficient 'improvement' when the installation of robots to control flow into the existing circle would have accomplished the task far less expensively and with far fewer adverse repercussions.

The traffic problem being addressed lasts no more than 4-5 hours a day on weekdays, during the morning, lunch-time and evening rush hours. 

The four-way intersection solution, as implemented at most other such intersections, creates a problem the other 19-20 hours a day when cars reaching intersections that are frequently devoid of other vehicles must incur brake wear to come to a stop, spew carbon into the atmosphere while idling at a red light, and then use fuel inefficiently while accelerating back to speed. 

That is, if drivers do not succumb to the temptation to run through a light as it turns red to avoid the potentially long wait while the robot cycles back to green, particularly when there's not another vehicle in sight.

The beauty of the circle with robots, as I saw implemented years ago in Nairobi, is that the lights go to a flashing amber cycle at all times other than rush hour, leaving drivers free to navigate circles with caution the same way they do at a circle without robots. 

During rush hour, all lights but one is red, with one approach at a time cycling to green.  With proper traffic research, the period of time each approach has the green light can be set to the typical volume of traffic coming into the circle from that approach, thereby reducing the chance of an uneven backup on any of the approaches.

So, Gaborone Traffic Department, please consider conducting an inexpensive traffic control experiment with portable robots on, say, the BTV Circle, before tearing up any more of our non-rush-hours-friendly roundabouts!

And while you're at it, how about studying traffic patterns to determine the best settings for the robots at existing four-way intersections? 

The standard robot pattern appears to be 'straight-ahead and right-turn', one at a time for each direction leading into the intersection. 

That's fine when there's a relatively even number of cars approaching from all directions and as many turning right as going straight ahead or turning left -- such as where the airport road crosses the Western Bypass.  But go one intersection north from there, near the Shell Filling Station', and you find 80% of the traffic going north or south, with very few turning right, and yet the robot cycles evenly for all four directions.  Traffic coming from Mochudi must often wait minutes while no vehicles cross the road from the east, more minutes while no vehicles cross from the west, and then still more minutes while no vehicles turn right from the south.

 At this and similar intersections, the robots should be retimed to stay green for both south- and north-bound traffic for perhaps 65% of the time, right turn only for both north- and south-bound traffic for 15% of the time, and 20% of the time for east- and west-bound traffic.

Sincerely,
Brent Schaeffer
Phakalane