Double Deckers vs Bendy Bus

My wife asked me what's the fuss and difference about having double deckers and bendy buses, since they are both high capacity buses.

While answering her, I thought I do a post on the question as well

Compared to single deckers which can take about 90 passengers, high capacity buses are a welcomed sign in the more and more crowded Singapore. It is more efficient to run per passenger and with a 35% more capacity than a normal single deck bus, it means 5 single deck sent out, 4 high capacity buses can do the job, with one less driver, less pollution and such.

For comparison in this post, representing double deckers will be SBS Transit Volvo B9TL ("B9TL" or "DD") vs SMRT Man A24 ("A24") which will represent Bendy / Articulated buses.

Volvo B9TL on SBST Service 240 

Image source: http://publictransportsg.files.wordpress.com/2013/04/240_blog.jpg

Man A24 "Mandy" on SMRT Service 190

Image source: http://publictransportsg.files.wordpress.com/2013/07/388_190-2.jpg

Here are a few things that I will consider

1) Max Capacity
B9TL-124 (53 Upper Deck, 27 Lower Deck, 44 Standing)
A24-131 (54 Seating, 76 Standing)

Score: B9TL DD: 1, A24 Bendy: 1 (Since both are high capacity, I think both should get a point.)

2) Boarding / Alighting
Boarding
In the DD, there are  2 routes, you either choose to go up to the upper deck or walk straight to the lower deck, there is a divergence of people which means less congestion (hence faster speed when boarding).
In the A24, you can only walk straight.

Alighting
Unloading is the more interesting part here as the DD has 1 door to exit while the A24 has 2 exit doors. So while alighting the A24 will be much faster than the B9TL. We talk about divergence of people while boarding, however the same point is a drawback the DD has when the direction is reversed. People from the upper deck and lower deck have to wait for the same exit door to exit, hence alighting is slower.

Score: B9TL DD: 1, A24 Bendy: 2

3) Occupied Road Space 
B9TL - 12m
A24 - 18.75m
If you have been at a bus stop with more than 8 services calling at the bus stop, you will know buses when they doesnt come, all doesnt come, but when they come, all will come together. So when 5 buses call at the bus stop, the first 3 could open its door but the next 2 will have to wait till the first 3 had finished their boarding and alighting

The scenario is usually made worse when the first 2 buses are bendies, because 18.75m x 2 = 37.5m compared to 12m x 3 = 36m, so 2 bendies take the space of 3 DD or Single Decks, which is no good for an efficient Public Transport system.

Score: B9TL DD: 2, A24 Bendy: 2

4) Comfort
I am not one who love standing on the bus, especially for long trips, so if we compare seating capacity, its 80 seats in total for B9TL vs 54 seats total for A24. Putting it in the other perspectives, 32 more passengers will have to stand if an A24 came instead of a B9TL. So for long trips (or a long enough trip at least) the DD wins in this respect.

Score: B9TL DD: 3, A24 Bendy: 2

Review, in my opinion.
SMRT, with their Enviro500 Double Decks and existing articulated buses,will have more flexibility in deploying buses based on the load of the particular service. Cross town services such as 969, 857, 190, 972 as well as SBS transit 161, 168 should have more DD since the passengers take from one town to another with not many passengers alighting frequently. Feeder services and certain intra-town services such as 851, 854, 961 should go for more bendy buses in their fleet as passengers board and alight at various bus stops along these routes.

SBST, with most its routes going through towns and neighbourhood, should consider buying Bendies to compliment the DD and also to have more flexibility.