From the Red Line
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From the Red Line

Taking water breaks

To cut a long story short, schedules matter in a new normal.

As readers know, I live in Bukit Panjang. That means service 976, one of the route operating the new Linkker opportunity-charging electric buses, is right at my doorstep, and is an alternative for me should I feel like not using the LRT.

Considering the fact that 976 was only introduced with the off-peak suspension of LRT service A, using this as an introductory step for Linkkers is interesting. Should the Linkker buses not be able to meet their reliability targets, 976 passengers can continue their journey on the LRT with some inconvenience. But from what I see, most people were already taking the LRT the long way anyway, which meant 976 is actually not that well-patronized.

Recall that electric buses are still on an experimental basis here. Making the most out of opportunity charging means we have to rethink how we run buses, in order to provide the short breaks during the day that the vehicles can recharge. Otherwise, the experiment is handicapped and not an equal comparison from day one, and we’d be better off hauling batteries across the island and changing over fleets in the afternoon. That’s the easy way out, but it wouldn’t be a fair review.

Like running a marathon

But even before the bus driver outbreak bringing down frequencies on such a little-used service, the punctuality of 976 has arguably been hit by the introduction of Linkker buses. Simply put, it appears that the charging strategy has not been fine tuned. Even if the previous trip arrives at Bukit Panjang late, it appears necessary to still cram in a few minutes of charging, with the driver remaining with the bus before beginning the next trip.

A camel drinking water (source: me)

The idea behind opportunity charging is that top ups can be done throughout the day in order to keep the vehicle on the roads more often, unlike the Chinese bus models which can run whereever they want at least until the battery runs out, and then the magic ends and it has to go home for charging. Naturally, the downside of opportunity charging is that the chargers need to be installed at the layover points, namely bus terminals.

High-wattage chargers have thus been installed at Bedok and Bukit Panjang interchanges to support Linkker operations. At 450kW, these high-wattage chargers have three times the wattage of the 150kW chargers installed at depots for the Chinese bus models — and with each depot charger being shared by two buses, that means a Linkker can charge six times faster than at a fully loaded depot charger. Along with the Linkkers having slightly more than half the battery capacity, it is thus claimed that a full charge will take only 10 to 15 minutes, getting the range to go 130km.

But is there, though, really a need to charge all the time? A significant amount of bus routes have single-trip distances below 30 km, which could let you get there and back again twice on a single charge — even if it’s not so necessary at some point in the future with widespread deployment of chargers at every single interchange.

EDIT: As can be seen in the replies, readers have told me this may happen for 976, and it may just be a matter of bad timing on my end. But if it still doesn’t take place for 176, then that’s some food for thought.

Pace yourself

Since there’s no charging at the CCK end, we must count both directions of Service 976 in length; that would be 17.6km according to Land Transport Guru. But also factoring in additional turning here and there in the depots, 18km per trip would be a good yardstick; that means 7 trips before needing a recharge and not counting any potential gains from regenerative braking.

One way trip times are stated to take 37–50 minutes, but since the route supposedly ran at 15 minute frequency at least before the outbreak, that should mean you need around 8 buses to operate the full route, with the time difference between arrival at one interchange and arrival at the other being approximately an hour. While only 5 Linkkers are deployed, for this operational analysis we’ll just say all buses used are Linkkers — just to illustrate what can happen if we want a new normal of opportunity-charging buses.

What might now need to happen is that either runtime is dragged out in order to produce the longer layover times needed to charge, all the more since time is also spent driving around the interchange, positioning the vehicle under the pantograph charger, and the technical time in deploying the charger. What might be a 10 minute layover ends up getting us only 5 minutes of productive charging time before it’s time to go.

Worse still, if the bus is already late to begin with, as what happened to me, and was one of the very rare times I saw a significant enough queue for 976. Without the need for charging after every trip, it would be possible for the driver to not take a break and just proceed directly to pick up the next batch of passengers, maybe stopping for a minute or two to the interchange office to check in. But with charging, a stop by the charger is pretty much obligatory, with all the technical time that entails.

With short routes, maybe in a pinch it could be possible to skip the charger — but then it falls on the driver or BOCC to make a judgment call and decide whether there is enough charge to skip the charger and come back next time — and perhaps also if the driver can make up the schedule enroute and finish the next round trip with some time for charging. The ability to send telemetry back to the BOCC might help, but decisions still need to be made on whether this is sustainable.

Pain points

“But yuuka,” you say, “the busfans forever complain about padded schedules. How can buses still be late?” Well, it is what happened. As I have long believed, schedule padding only does so much when the roads are busy with evening peak commuters heading home and the neighbourhood feeder becomes a victim of congestion, with little or any headroom for an experienced driver to gain speed in one area so that the bus can still reach the terminal on time. The decision could come out that they need even more padding, and that if there’s additional layover time to charge, all the better.

The more important bit may yet be to ensure that routes are not too long, in order that a single trip can be completed with 5 minutes of charging at most — that would mean a maximum round trip distance of 40–50km. I’ve said this before and I’ll say this again — by shifting longer distance trips to the MRT system and breaking up the cross-country trunks, shorter round trips can be performed, which provides far more flexibility, including with charging.

Why not faster chargers? 450kW is probably as good as it gets since that’s the maximum supported by the OppCharge standard. Furthermore, adding additional high-wattage chargers may tax the local power grid. The rate at which they’re adding low-wattage car chargers might spell something for the feasibility of many high-wattage chargers at interchanges. With a larger rollout, a bus could well arrive at the interchange to find all the charger positions in the layover area full — but that might then be the problem of the scheduler, requiring a lot of coordination between operators to minimize the issue from the root.

Or there may be another solution. Offhand, I would argue that there’s an additional inefficiency in our bus interchanges we could take advantage of if we do decide on a bigger rollout of opportunity charging vehicles. Boarding only from the front takes up quite a fair bit of time — it may not only happen at interchanges, but also key transfer nodes linked to MRT stations and the like. Placing charging stations at these points may prove to be a better idea, taking advantage of the additional time from inefficient passenger exchange to charge the bus. With some enroute charging points, it could then be possible to take that risk.

Another option might even be to specify electric buses with roof-mounted solar panels. That way, the solar panels could come in useful to supply additional power demanded by the bus especially on bright and sunny days. But like regenerative braking, it’s not entirely a given and should not be relied upon by schedulers due to the weather.



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Sometimes I am who I am, but sometimes I am not who I am not.