Onboard the SL4: The Superloop Detached from the Loop

Go Ahead Blue Triangle BYD BD11 at Canary Wharf

Welcome back ladies and gents. In this post, you're joining me at Canary Wharf, London’s gleaming financial district, where skyscrapers tower over the Thames and people smelling like bank notes. This bustling hub isn’t just the heart of global finance (or the symbol of capitalism), it’s also the starting point for the SL4, one of the newest routes in London's Superloop bus network.

Superloop Map, 2026 (Source: https://tfl.gov.uk/cdn/static/cms/images/superloop-map-large-all-routes.png)

Introduced by TfL (Transport for London) in 2023, the Superloop is a network of limited-stop express bus routes expected to make travelling around outer London faster and easier. Rather than having passengers travel through central London, the network links major town centres, transport hubs, hospitals and shopping areas with fewer stops than regular bus routes. While some services were created specifically for the Superloop, others were existing express routes that were rebranded, such as the 607 (Uxbridge - Shepherd's Bush/White City) becoming the SL8 and the X26 (Croydon - Heathrow Airport) becoming the SL7. The network was completed in 2024, forming a near-continuous orbital route around the capital. Although each route operates independently and passengers may need to change buses to complete longer journeys, the Superloop has become one of TfL's flagship bus initiatives, offering faster, more convenient travel across outer London and providing an attractive alternative to driving.

Being one of the most significant additions to the network is the SL4, only began running from April 2025, connects Canary Wharf with Grove Park via the Silvertown Tunnel. Unlike some Superloop routes that simply replaced existing express services, the SL4 was introduced as an entirely new route to provide a fast cross-river connection in east London. Before the Silvertown Tunnel opened, passengers travelling between these areas often faced lengthy journeys involving changing at central London or the congested Blackwall Tunnel. By taking advantage of the new tunnel, the SL4 can provide a much quicker and a more direct journey between outer London destinations without the need to changing at central London. Now you may have noticed that the SL4 is the only superloop bus route that isn't actually connected to the main loop formed by SL1,2,3,5,7,9, and 10 (other than the Bakerloop BL1, but even so it's connected to the peak hour service SL6), nor does it connect to a different superloop bus that connects it to the loop. 

EBD73 at West India Avenue (Stop D) 

Anyway, you now join me at West India Avenue, where the SL4 starts on a lovely Saturday morning under the glamorous London sun. The SL4 normally starts at Stop C (on the eastbound side of the avenue), but the stop was closed for roadworks, so I crossed the street to Stop D, where the SL4 usually parks for layovers, assuming the service would start there instead. The driver initially told me I should board at Canary Wharf station, as the usual stop was closed and that was where the route would officially start, but she kindly let me board the bus there anyway. Before we set off, I had a lovely chat with her. After admiring the new swimming pool down by the Thames (hopefully the water isn’t drawn straight from the river), she learned that I’d come up from Exeter and remarked on how spoiled Londoners are. She reckoned they should try living in Exeter for a while, where buses can leave you waiting an hour or two. She also mentioned a friend in Colchester, where house prices are significantly cheaper than what she pays in the Docklands. It was certainly a nice reminder of how different life can feel outside London, even for someone like me who came from the massive, crowded sweatbox known as Hong Kong. Back in Exeter, buses really can leave you waiting an hour or more, so her point certainly landed. At the same time, hearing about Colchester’s house prices made me wonder whether the convenience of living in the Docklands is always worth the cost. It must be quite a trade-off to pay a premium just to live within easy reach of central London, especially when places a little further out can offer considerably more space for the same money. I suppose that's one of the compromises of London life. You pay through the roof for convenience, while a longer commute can buy you a much more affordable home. Conversations like this are one of the small pleasures of taking the bus instead of the Tube. You never quite know who you’ll end up chatting to.

BD11 Lower Deck

Hopping aboard Go-Ahead Blue Triangle's EBD73, a 2025 BYD BD11 electric double-decker. Unlike the older and more common BYD D8UR-DD, which uses ADL Enviro400 City bodywork mounted on a BYD's chassis, the BD11 is an integral bus, which means that both the chassis and bodywork are designed as part of a single vehicle by BYD. It also represents a newer generation of BYD’s electric bus technology, if you look underneath, it uses BYD’s revolutionary Blade Battery, a lithium iron phosphate (LFP) battery made up of long, thin cells that are that offer strong resistance to thermal runaway (apparently you can puncture it with a nail and it wouldn't catch fire or explode). The bus is also fitted with hairpin motors embedded into the wheel hub (rear axle only), which uses tightly packed rectangular copper windings to improve the use of space inside the motor and increase its power density. The electric drivetrain also uses silicon carbide (SiC) power electronics, which vastly improves the efficiency of the powertrain. So, as you can see, this 14-tonne giant is equipped with the latest, fanciest tech there is available.

BD11 Upper Deck

Front Row Seats

USB charging ports and the stop bell

After settling into the front row of the upper deck, I immediately noticed the two roof windows letting in extra natural light, which I always appreciate (probably more than the windowed staircase, which isn't found on the BD11). The seats are fairly comfortable; a bit stiff, in my opinion, but nothing like the Thameslink "ironing board" seats. In front of the seats is a USB charging point featuring both Type-A and Type-C outlets, alongside a stop bell. Having a Type-C port is always a welcome addition, especially as most devices are switching over due to EU regulations. 

Route map of SL4

Illustration of route diversion

We set off from West India Avenue at 10:02. Because the original stop and that section of road were closed, we headed down Westferry Road instead of looping around Westferry Circus. We then turned left onto Bank Street, passing Jubilee Park (where you catch the Jubilee line), before heading onto Upper Bank Street toward Canada Square Park. From there, we turned left onto South Colonnades, where westbound buses normally stop, and looped around Cabot Square to North Colonnades, the route's official starting point. I have included a map of this diversion in case you are interested, as navigating the dense roads of Canary Wharf can get confusing. However, since the official start is Canary Wharf station, most passengers board there (and were expected to) instead of doing a massive loop around the wharf like I did. Luckily, the driver was kind enough to just let me hop on, saving me a 4-minute walk back to the station.

Trafalgar Way Eastbound

Diverting via Aspen Way as Blackwall Way is closed

We departed Canary Wharf station at around 10:05, heading east along Trafalgar way towards Billingsgate Market, where the famous traffic light tree is also located. We then made our way around the massive roundabout by Blackwall DLR station, and reached the Baffin Way bus stop, where the driver announced our second diversion of our journey that will take us directly to Leamouth instead of stopping at stops along Blackwall Way, including East India DLR station due to utility works. So, we circled back to the massive roundabout via Yabsley Street and Prestons Road, and headed onto Aspen Way, heading directly towards Leamouth.

Footbridge across Aspen Way leading to East India DLR Station

LCD PIS screen located at the front of the upper deck

Canary Wharf-bound SL4 at Leamouth

We arrived at Leamouth Orchard Place at 10:21, where we're greeted by a SL4 in front of us heading the other direction back to Canary Wharf. Just north of the stop is London City Island, where the most fancy and expensive housing estates are located, with a bridge across the river lea connecting the estate with canning town station (apparently, it's also home to the English National Ballet, if you're interested in that). We continued our journey after a few passengers got on and off (the bus wasn't very busy, only one or two passengers on the upper deck excluding me) and made our way to the Silvertown tunnel.

Silvertown Tunnel

Inside Silvertown Tunnel

The Silvertown Tunnel, which opened relatively recently in April 2025, provides an alternative crossing over the Thames, relieving the already congested Blackwall Tunnel. For some reason, the tunnel doesn't permit cyclists, so TfL has had to operate a dedicated cycle shuttle bus through the tunnel instead, allowing cyclists to take their bikes on board and cross the river onboard. You don't need me to tell you that no one actually uses this service and it's costing TfL a load of money to operate. If you're wondering where your tax money is going, well here's one answer for you (If you live in London, of course.)

Running Express on the A102

Shooters Hill Road (Stop D)

We emerged from the tunnel at Greenwich Peninsula shortly afterwards and joined the A102, which originally served the Blackwall Tunnel, now having to deal with traffic from Silvertown tunnel as well. We ran non-stop through to Blackheath, where we left the A102 and turned onto Shooters Hill Road, marking the end of the express section of the journey. From this point onwards, we would be stopping at every stop all the way to Grove Park.

The Heath along Prince of Wales Road

We continued through the heath, plunging into this massive open space in southeast London. I’d only ever passed the heath on a 108 bus years ago (back when the Mercedes Citaros were still in service), and that was at night, so I never really got a proper view of it. Seeing it in broad daylight this time, however, really impressed me. It’s quite remarkable to find such a huge expanse of open grassland in the middle of southeast London, especially after spending so much of the journey surrounded by buildings and busy roads. 

Central Blackheath

Lee Road

We arrived in central Blackheath after just around 30 minutes from Canary Wharf. Unfortunately, there wasn't much time for me to admire the sights around central Blackheath, as we headed off almost immediately after making a brief stop at Blackheath Station. From there, we continued on our way towards Lee. 

Lee Station Bridge

Westhorne Avenue (Stop D)

We reached Lee station just 5 minutes after leaving central Blackheath, with a Southeastern City Beam train giving us a rather nice greeting as we passed underneath the station bridge. Traffic seemed to catch up with us on Westhorne Avenue, but fortunately the delay cleared quite quickly. Before I knew it, we had turned onto Baring Road for the final stretch towards Grove Park. 

Baring Road

Next Stop Announcements

Grove Park Bus Station Alighting Stop

We whizzed along Baring Road relatively quickly, as there weren't many passengers getting on or off, and were soon greeted by another SL4 heading in the opposite direction. It wasn't long before the next-stop announcement called out the final stop of our journey, Grove Park Bus Station. We arrived at 10:50 am, exactly 48 minutes after leaving Canary Wharf. I was dropped off at the alighting stop on Baring Road, Stop A, while the bus continued into the bus station itself and pulled into one of the layover bays, where it would wait for its next journey back towards Canary Wharf.

EBD73 parked at Grove Park Bus Station

BYD B12D (Bus launch event at Queens Hill, Hong Kong in Aug 2023)

And with that, my first ever journey onboard the SL4, both the route and the BD11, came to an end. From the banknote-smelling streets of Canary Wharf, through the new Silvertown Tunnel and across the mighty heath of Blackheath, all the way to Grove Park, it was, I'll be honest, quite an interesting 48-minute ride. The BD11 is fairly comfortable to travel on. Like any other electric bus, it is smooth and quiet, and it also comes with air conditioning. Unfortunately, its effects weren't particularly apparent that day. It was quite warm, yet the dedicated vents on top of my seat wasn't blowing out much cold air, and I suspect the open windows did more to keep the bus cool than the air conditioning system. I've long had a problem with the air conditioning on BYD buses, having experienced the BD11's close relative, the B12D, in Hong Kong. On those buses, the air conditioning can be practically non-existent, which is a pretty serious problem when you're roaming around a massive oven like Hong Kong.

Grove Park Station

As for the SL4 itself, I think it is a genuinely useful addition to the network. The journey from Canary Wharf to Grove Park was reasonably quick, and the Silvertown Tunnel certainly makes this part of southeast London much more accessible by public transport. Without the SL4, travelling between Canary Wharf and Grove Park would likely involve changing in Lewisham, adding more time and cost to the journey. Just like any other London bus, a single fare on the SL4 is £1.75, which is certainly cheaper compared to going by train. The route also offers quite a varied scenery, going from the skyscrapers of Canary Wharf to the unique landscape around Blackwall, then through the massive heath of Blackheath before finally settling into the suburban streets around Lee and Grove Park. The only slight disappointment is that once we reached Blackheath, the “Superloop” experience felt a lot less super, with the bus making considerably more stops and behaving much like any other local service. Still, I enjoyed the journey. Though why the SL4 terminates at Grove Park instead of heading another 20 minutes south to Bromley, where it could connect with the SL3 to Bexleyheath and Thamesmead and the SL5 to Croydon, is an interesting question. I can guess at a few practical reasons: Journey times would stretch beyond the ideal “express” window, and demand between Grove Park and Bromley might not yet justify it. But it still feels like a missed opportunity to connect to a proper southeast London hub. If TfL ever extends it, or if there’s a good operational reason I’ve overlooked, I’d love to hear it in the comments. 

Anyway, what are your thoughts on the SL4 or the BD11? Have you been on either of them? Let me know what you think in the comments below! As always, have a wonderful rest of your week, take care of yourself, and I'll see you in the next post.