It's been interesting watching the latest petrol price hike in Melbourne. There's usually up to 4 days before the new higher price moves across the market. Normally I see the price hike on the second of the four days and alert everyone using the Petrol Price Melbourne site www.PetrolPricesMelbourne.com.au. This time I noticed the price hike very early since I'm now recording prices in the area.
Two things became apparent. The trend on the site can go in any direction on the first day. Whilst some prices are spiking, others are still going down. It is really weird to watch part of the market going down whilst another part is having a massive price hike of around thirty cents per litre.
The second was I felt the colour coding for the markers on the maps which help people locate lower priced petrol wasn't particularly good. My initial approach was 21 coloured markers at set price intervals, but unfortunately this approach didn't make it easy to distinguish the cheaper prices as the prices move down. This is because the market has a small spread of prices (4-6 cents) so the markers all look very similar.
I decided to change the markers to indicate one cent differences. This is very good when prices are going down. When prices are going down the range of prices is usually between 6-10 cents, so the coloured markers can be easily distinguished. When the price spikes the average moves towards the middle so is everything lumped into red (expensive) and green (cheap). When this occurs you may need to check individual markers or use the cheapest page to find the cheapest petrol. When the price peaks the new peak becomes the average which will show as yellow. As prices drop the range increases and the range of coloured markers again increases.
I hope this new colour coding scheme makes it easier for people to find cheaper petrol and save money on their petrol purchases.
Kelvin Eldridge
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