Can I have a postcode to postcode drive time and distance lookup table?
With online mapping data increasingly accessible to the public, journey planning seems easier than ever. However, once you move beyond individual journeys to look at onward travel, planning for a fleet of vehicles, or a network of locations, things quickly get complicated. One question new clients often put to us is “Can we have a simple table of travel times between each postcode?” Unfortunately, this seemingly “simple” question comes with some significant challenges.
When do you need it?
There are almost 2.6 million postcodes in the UK (2,586,191). This means to do a postcode to postcode lookup you would need that many results squared, that’s almost 6.7 trillion (6,688,383,888,471) variations! How long would it take to produce the drive time and distance lookup tables for this? Well, if we assume it averages just one second to calculate the best time and distance between each postcode we can calculate the compute time needed to generate our data. 6.7 trillion rows will take 6.7 trillion seconds at one second per postcode to postcode pair. A year is just under 32 million seconds (31,536,000).
This means that the pure compute time is over 200,000 years (212,087 years to be exact)!
To allow for variations in travel time for peak, off-peak, HGV, and shortest distance driven (irrespective of road or traffic conditions), we’d need 4 calculations, so we are looking at a compute time of 800,000 years for a single end to end process. Using more computers can speed it up:
- If we have 4 computers, one for each task, we would have needed to start processing when the first homo sapiens appeared.
- If we can speed the process up to 10 per second by using better code, we could have started processing 20,000 years ago as the people in China invented pottery.
- 10 computers per task (not forgetting there are 4 results to calculate) and we could have started the processing as the Emperor Tiberius began his rule.
- 100 computers per task; we could have started the processing whilst reading Miss Austen’s new novel Emma, straight off the press.
- 1,000 computers per task and we could have been listening to Firestarter by The Prodigy when it was at number 1 in the charts.
- Would 20,000 computers be enough? No. It would still take a year! To get a real time process we would need 200,000 computers and it would still take 5 weeks to process all 4 sets of data.
What’s your budget?
Now we have an idea about how long it would take to produce postcode to postcode drive time and distance tables, how much storage space do you think we will need?
The sector to sector table is about 15Gb and has 123 million rows. Our postcode to postcode table is 54,000 (54,118) times as big. This means our new data table in an unindexed form would be 774,593 terabytes or 756 petabytes (812,219,753,484 Mb).
Up to 2014 Google had indexed about 200 terabytes of data. Our one data table is 400 times as much data as Google has handled in 16 years.
There is a 60 terabyte disk available. We would need 13,000 of them, they are expected to retail between $30,000 and $40,000 each, so lets be optimistic and say $390 million in total. They would draw power at 1 watt per terabyte so we would need a power station producing 770 MW to keep just the disks running (about a quarter of the output of a new nuclear power station, that retail at around £20 billion each).
A realistic yet accurate alternative
So it would seem that postcode to postcode data tables are a non-starter. Fortunately, we have an alternative solution that can return time and distance for any 2 postcodes in less than 2 seconds. Our TimeTravel product offers postcode sector to postcode sector drive times and distances for all of the UK without the massive amounts of infrastructure or forward planning we’ve previously described. We also update the system as new postcodes and road networks alter the calculations to keep it accurate.
The TimeTravel data table has distance and time values for peak, off-peak, HGV and shortest distance driven (irrespective of traffic conditions or time of day). It even accounts for Ferry crossing times, where travel to that part of the UK goes over water. To process all combinations takes days, rather than thousands of years, and we provide regular updates to our clients so that their customers and fleet drivers have the most accurate drive times available within seconds.
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