I have recently been able to compare two of the newest automated metro systems in the world, both connecting a major airport to a world city.

There are fascinating contrasts and similarities between Vancouver's Canada Line and Dubai's metro.

Service to Vancouver airport is more frequent and has smaller trains. Canada Line runs 2-car trains every 6 minutes, compared with Dubai's 5-car trains every 10. Vancouver has longer hours of service - a definite plus for a light metro system likely to carry airport-based employees.

Train interiors and exteriors are very similar. Both systems are obviously new, modern, clean, light, bright, airy, comfortable and with space for luggage, buggies and wheelchairs.

Dubai's has two classes - the car at the city end of each train is in two halves, with the front half for Gold Class passengers and the rear half for women and children only.

There is, however, little to choose between the accommodation in the two classes - which rather vindicates my own personal view of first-class train travel. This is that people pay extra to travel first class for one main reason - which is to travel with other people who have also paid extra! As a railwayman of long standing, my advice is always to provide it if it's culturally acceptable: some people are willing to pay extra, so take the money!

Both services provide a very smooth and comfortable ride.

Not all stations on the Dubai system are open - including the one serving Terminal 1, which is still being worked on.

Both serve stunning airports.

Dubai's Terminal 3 is a visual feast of glass and marble, with a beautiful garden area by the station - although sadly not in a place where many train travellers will see it.

However Vancouver Airport is more vibrant with trees, waterfalls and First Nations art throughout the building.

Vancouver Airport Authority invested in the railway and it shows: the stations on the island housing the airport are of a significantly higher quality than those on the mainland. Many stations have self-service check-in machines. Stations in Dubai are of a uniformly high quality - they have been compared to the lobby of a 5-star hotel, and it's a good comparison!

Dubai is clearly a country unused to public transport: a lot of people using the system are really just going for a ride (and why not - they paid for it!). To a lesser extent this happens in Vancouver too, especially since the airport has very wisely opened an excellent viewing lobby, with good access to the wide range of landside shops and cafes.

Vancouver can't compete with size for Dubai - it has a single platform on a single line at a terminus, whereas Dubai's Terminal 3 station is on a through line of a twin-track railway with two platforms (and these, like Hong Kong's, are on different levels to make it easier for passengers to reach the terminal - although there isn't level access for both arriving and departing passengers as there is at Chek Lap Kok).

Ticketing is possibly the least good part of each - some temporary signage at Vancouver Airport shows some passenger confusion, and in Dubai there are just too many options!

But that is really groping for faults: both services are excellent - and well used.

There is a theory around that 2+3 seating on trains - where there are 2 seats on one side of the centre aisle and 3 on the other - isn't worthwhile because no-one uses the middle seat of the three and therefore it is wasted.

Er - really? Where has this phenomenon been observed? Not on the trains I commute on! If there is a seat, it gets sat in - and if there is a seat with a bag on it, the bag gets moved!

It is, of course, true that the centre seat is unpopular and the last to be filled. But it's better than no seat!

If the journey is very short - 5 to 10 minutes - OK, people may choose to stand by the door rather than taking the trouble to find a seat. But even on a 20 minute journey - yes, if the load factor approaches 100%, the centre seats get sat in.

I can't help closing with the recollection of a journey last week when I did have to sit in the centre seat of a three. The aisle and window seats were occupied by quite big men, and the bloke by the window was taking up quite a lot of space. I did wonder, having sat down, whether or not I was actually touching the seat at all or just supported by these two guys on either side!