That’s the one that lets you sail through traffic junctions with every light in your favour. Is it for real? Here’s your guide to GLIDE!

Tapping on technology to surf the roads smoothly isn’t stuff of the future. LTA’s Green Link Determining System (GLIDE) aims to make your commuting dreams come true.

How does GLIDE work?

The GLIDE system adjusts the timing of the green light at traffic junctions as traffic flow changes. It allows adjacent traffic signals to sync up in such a way that your number of stops is minimised.

GLIDE’s principal purpose is to minimise the overall delay for all commuters. When traffic builds up, the lights adjust to maximise throughput and minimise jams. If you are travelling along major corridors and arterial roads, you might have noticed the difference! Waving you through is one of the aims of the system.

The evolution of linked traffic lights

As it turns out, the idea of a “green wave” for traffic isn’t new at all! In fact, this has been a work in progress for decades.

Early 1970s:

The first 36 traffic signal controllers were linked by cables laid under footpaths, to create a couple of “corridors”. Two pairs of one-way streets were connected to a master electromechanical controller and worked using an assumed vehicle speed and a fixed cycle time*.

Late 1970s:

Microprocessor controllers were the latest tech! With no more need for physical cables to connect the traffic lights, more corridors could be linked. Controller clocks were synchronised to cue the green lights, but tended to drift out of sync. 

Early 1980s:

Area Traffic Control was installed, taking advantage of existing telephone cables to link a central computer to 181 traffic signals. This fixed the drifting clock cycle problem and the control centre could manage and monitor the lights, but it couldn’t cope with changing traffic conditions. If a jam built up because of road works or an accident, you’d still get stuck.

1988:

SCATS (Sydney Coordinated Adaptive Traffic System) was adopted to replace the fixed time system and given the name GLIDE in Singapore. Wire loops implanted 25mm under the road surface near the stop line detect vehicles, counting both their number and the gap in time between successive ones. GLIDE then works out the optimal cycle times to keep traffic moving and allocates green time accordingly.

Fun Facts: All About the GLIDE System

1. Which roads in Singapore currently use GLIDE?

All of them! Today, every traffic signal on the island is controlled by GLIDE — that’s about 2,700 intersections. A regional computer controls up to 250 intersections. With 18 regional computers on the job, we can potentially manage 4,500 junctions!

A central computer monitors the operation of each regional computer.

2. Is the green wave adjusted in real time?

Yes. GLIDE is at work 24/7!

3. Does it break the chain when someone activates a pedestrian crossing?

No. Pedestrian lights are part of the GLIDE network. If no one presses the crossing button, the lights won’t change—this way motorists won’t be caught at an unnecessary stop.

4. If there is a green wave, would there also be a red wave for unlucky motorists?

The green wave favours the heavier traffic flow, for example city-bound traffic in the mornings and home-bound roads in the evening. If you’re headed the other way, your best bet to catch a wave is to keep with the main stream of vehicles, as GLIDE factors in the gaps in the flow. If you’re too far ahead or behind, you won’t be “counted” and miss the wave!

5. Then is there a particular speed I should be driving at in order to stay on the “wave”?

Nope, GLIDE looks at how heavy the traffic is, not how fast it is going, when it computes how to allocate green time. Like we said, stick with the crowd and just go with the flow!

Motorists should always observe speed limits when driving and follow driving safety rules.

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