Traffic Operations Frequently Asked Questions
- What criteria is used to determine new signals?
- How does a traffic signal know if a vehicle and/or pedestrian is present?
- Is it really necessary for me to push a button to activate the pedestrian signal? Why do some signals, which have pedestrian displays, show a 'Dont Walk' indication even when the signal is green for the side-street (minor road)?
- I get half way across the street and the 'Flashing Don't Walk' indication appears. Do I still have enough time to complete my crossing?
- Why does the Left-turn Green Arrow sometimes work, and other times not?
- I have to wait a long time to turn left because the existing left turn green arrow is too short. Why can't the City allocate more green time to the left turn green arrow so that left turn delays can be decreased?
1. What criteria is used to determine new signals?
Traffic and pedestrian signals are implemented on a warrant system, based on the guidelines of the Transportation Association of Canada (TAC) . The City performs turning movement counts at major intersections and applies these numbers to the warrant process. The highest scoring intersections are considered for traffic signals.
Other criteria that are used to determine the need for traffic signals include; delay to side street traffic, collision history, pedestrian activity/delay.
The City of Kelowna employs some of the most technically advanced traffic signal hardware (traffic controllers) available. All City traffic signals, except for the intersection of Bernard Avenue/Water Street, are fully-actuated. Fully-Actuated signals have vehicle detectors for all traffic lanes and pedestrian push buttons for all crosswalks. Full-actuation allows the signal controller to apply green time to the highest demand, even if that demand changes throughout the day.
2. How does a traffic signal know if a vehicle and/or a pedestrian is present?
Vehicles are detected by electromagnetic wires (loops), which are imbedded in the pavement, behind the stop line. Video detection is also widely employed. Video detection allows greater flexibility if there are intersection changes. The size or location of the detection zone can be changed or we can add/delete lanes and there is no possibility of wires in the pavement breaking or being cut.
Pedestrians are detected by the pedestrian push-buttons. When pushed, a message is sent to the traffic controller, requesting a change to the signal indication and to bring up the pedestrian walk signal and allow pedestrians sufficient time to cross the street. The button only needs to be pushed once. Repeated pushing will not expedite the walk phase. The walk indication will only come on after the current green phase is serviced unless there is no call to the side street.
3. Is it really necessary for me to push a button to activate the pedestrian signal? Why do some signals, which have pedestrian displays, show a 'Don't Walk' indication even when the signal is green for the side-street (minor road)?
The light for the vehicles and the pedestrian indication operate independent of each other. If a pedestrian has not pushed the button, the pedestrian walk phase will not come up. At fully actuated intersections, a pedestrian must push one of the pedestrian push buttons to receive a "Walk" signal. When a button is pushed, a pedestrian will receive a "Walk" signal with sufficient time to cross the major road. If a button is not pressed and the traffic control signals respond to a vehicle only, a green signal will be displayed along with a "Don't Walk" indication for pedestrians. The length of this green signal will likely be considerably shorter than the required walk time for a pedestrian because the length of the green signal is variable, based on the vehicle demand only and vehicles don't take nearly as long to cross the intersection.
We use this type of operation to maximize the efficiency of the intersection. It serves to minimize delay for the relatively heavier volume of traffic on the major road. It is the City’s practice to always install pedestrian information signs, which describe this operation at these types of intersections.
4. I get half way across the street and the 'Flashing Don't Walk' indication appears. Do I still have enough time to complete my crossing?
Some pedestrians misunderstand the “Flashing Don’t Walk” or "Helping Hand" display feature. This feature is intended to warn pedestrians who have not started to cross that there is not enough walk time left to start and complete their crossing safely. If they have started to cross and the "Helping Hand" indication appears, there is still sufficient time to complete their crossing. The duration of the "Helping Hand" indication is included in the calculation of the pedestrian walk time. Where this feature is installed, it is augmented with information signs to explain the operation.
Pedestrian walk times are calculated based on the walking speed of a typical adult (1.2 metres per second). At locations with high percentages of senior citizens or children, walk speeds are reduced to 1.00 metres per second to accommodate a slower walking speed.
5. Why does the Left-turn Green Arrow sometimes work, and other times not?
Left-turn advance signals can be programmed to operate during specific periods of the day but typically will come up based on traffic demand.
6. I have to wait a long time to turn left because the existing left turn green arrow is too short. Why can't the city allocate more green time to the left turn green arrow so that left turn delays can be decreased?
The development of signal timing is a delicate “balancing act”, where the City tries to allocate movement fairly to all directions, based on typical and observed demand. In some cases, the City would prefer a longer left-turn priority feature but often is constrained by high traffic volumes arriving at the intersection from other directions. For instance, if we add more time onto a left-turn priority feature we must remove “green” time from other traffic movements. After all, a sixty second cycle length only has 60 seconds, regardless of how it is allocated. Think about it this way; in 10 seconds we can typically accommodate four left-turning vehicles. If we are holding up two lanes of opposing traffic, this same amount of time applied to that through traffic can accommodate up to 12 vehicles.
If I back up and drive forward again, the signal will change quicker - This does not work. Once you trigger the detector, it tells the controller that you are waiting. Nothing else is required.
If I get out of my car and push the pedestrian button, the green light comes on quicker – If the traffic control signals are functioning properly, the pedestrian push-button does not make the green indication appear sooner. However, it can make the green light longer at some signals, since the pedestrian walk time is usually longer than the green time. However, this also causes extra delay to the traffic on the other approaches.
Vehicle detection is by pressure or weight sensor - this has never been the case. The cuts in the asphalt are for the 'loop' detectors. Loop detectors are very sensitive and will also detect bicycles if they are above the wire, not in the centre of the loop. You must be behind the stop line in order to activate this detector.