The Anonymous Widower

Along The Hope Valley Line – 13th July 2020

These pictures show my return trip between Manchester Piccadilly and Dore & Totley stations.

There are an assorted set of stations.

  • Some stations appear to have new platforms.
  • Marple station has a impressive step-free bridge.
  • Some stations may be Listed or should be.
  • There are walking routes from some stations.
  • Some stations need improvements to the access.

I also have some thoughts on the service.

The Class 150 Trains

The Class 150 trains have these characteristics.

  • Installed Power – 426 kW
  • Weight – 35.8 tonnes
  • Operating Speed – 75 mph.

This compares with these for a Class 195 train.

  • Installed Power – 780 kW
  • Weight – 40 tonnes
  • Operating Speed – 100 mph.
  • Acceleration – 0.83 m/sec/sec

Unfortunately, I can’t find the acceleration for a Class 150 train, but I suspect that it’s not as good as the Class 195 train.

  • I was in a Class 150 train, for both journeys.
  • IThe train was on time both ways.
  • The engine under my carriage wasn’t working that hard.
  • The train was trundling around at around 60 mph.
  • The operating speed of the line is 90 mph.

So I suspect, that a well-driven Class 195 train will shave a few minutes from the journey time.

Transport For The North’s Plan For Manchester And Sheffield

Transportbfor the North objective for Manchester Piccadilly and Sheffield stations can be summed up as follows.

Four tph in forty minutes.

As current trains take over anhour, it could be a tough ask!

The Timetable

The timetable isn’t very passenger-friendly with no easy-to-remember clock-face timetable.

This must be sorted.

Hopefully, it will increase the number of passengers riding on the route.

Battery Electric Trains

Consider.

  • Sheffield station will be electrified for High Speed Two.
  • It is likely that the route between Dore & Totley and Sheffield station will be electrified.
  • There is electrification at the Manchester end of the route.
  • The distance without electrification in the middle is probably about thirty-six miles.
  • Fifty-sixty miles seems a typical range quoted for a battery electric train by train manufacturers.

As electric trains generally accelerate faster than their diesel equivalent, these could run the route reliably and save time on the journey.

Conclusion

I’m coming round to the opinion, that Transport for the North’s objectives for the route can be met without electrification.

July 14, 2020 Posted by | Transport | , , , , , , , , , | 2 Comments

Beeching Reversal – Sheaf Valley Stations

This is one of the Beeching Reversal projects that the Government and Network Rail are proposing to reverse some of the Beeching cuts.

Stations To Be Rebuilt

As you approach Sheffield station, you pass four station sites, three of which are demolished and the fourth is just a shadow of its former self.

Dore & Totley

Dean & Totley station used to have four platforms and this Google Map, shows what is left after British Rail’s vandalism in the mid-1980s.

Note.

  1. The station has only one platform.
  2. The single track in the platform handles all trains to and from the Hope Valley Line.
  3. At present it appears to be two trains per hour (tph) in both directions.
  4. The two tracks at the right are the Midland Main Line.

Transport for the North wants to run four tph between Manchester Piccadilly and Sheffield through here, that will take forty minutes between the two cities.

Updates planned for the station include.

  • A second platform for Manchester-bound trains.
  • A new bridge with lifts.
  • Platforms long enough to take a pair of Class 185 trains or a five-car Class 802 train.
  • A full hourly service.

There certainly seems to be enough space for another platform and track through the middle of the station.

At some point in the near future, the two Midland Main Line tracks will be electrified, as part of the upgrade for High Speed Two.

Between Dore & Totley And Beauchief

This Google Map shows a typical section of the line between Dore & Totley and Beauchief stations.

Note the two Midland Main Line tracks on the right and single-track to the Hope Valley Line on the left.

It would appear that the fourth track can be squeezed in between the single track and the Midland Main Line.

Beauchief

Beauchief station used to have four platforms before it was demolished.

This Google Map shows the station’s former location.

Note.

  1. The building with the red dot is the former Beauchief Hotel. which was by the station.
  2. On a larger screen you can see three tracks going into Sheffield.

I’m fairly certain that four tracks and two platforms for a station can be fitted into this narrow trackbed.

Millhouses & Eccleshall

Millhouses and Eccleshall station used to have four platforms before it was demolished.

This Google Map shows the station’s former location.

Note.

  1. Wikipedia says the station was accessed from the Archer Road bridge, which is in the South East corner of the map.
  2. It looks like there are three tracks with space for four.
  3. The road to the North-West of the railway is called Old Station Road.

As at Beauchief, it will be tight.

Heeley

Heeley station used to have four platforms before it was demolished.

This Google Map shows the station’s former location.

Note.

  1. The red arrow indicates Heeley Bridge, which Wikipedia says is near the station site.
  2. There appears to be only two tracks through here.

It is easy to follow the tracks from here to Sheffield station.

Could A Four Track Railway Be Rebuilt Between Dore & Totley And Sheffield Stations?

I’ve not seen anything that says that building a four-track railway through here is not possible.

In a few years, there could be the following tracks and platforms, on this section.

  • Two fast tracks for High Speed Two, Midland Main Line and CrossCountry trains, that will be electrified with 25 KVAC overhead electrification.
  • The High Speed Two trains will be classic-compatible and up to 200 metres long.
  • The two fast tracks will not have any platforms.
  • Two slow tracks for local services, that will be appropriately electrified.
  • The slow tracks will have step-free platforms, that will be long enough to take a five-car Class 802 train or a pair of Class 185 trains.

I can’t for the life of me understand, why this stretch of four-track main line between Dore & Totley and Sheffield stations was ever simplified, as at other places on the UK network, extra tracks were being added to the main lines, at the same time.

Future Services On The Fast Lines

Currently, the following services take the fast lines between Sheffield and Chesterfield stations via Dore & Totley station.

  • East Midlands Railway – Sheffield and London St. Pancras – 2 tph
  • East Midlands Railway – Sheffield and Norwich via Nottingham – 1 tph
  • CrossCountry – Edinburgh/Newcastle and Derby/Birmingham and the South – 2 tph
  • Northern – Sheffield and Nottingham – 1 tph

That is a very modest six tph.

High Speed Two are currently planning to run two tph between Sheffield and London Euston.

There may or may not be other changes.

  • As Birmingham Curzon Street and Sheffield will be just forty-seven minutes by High Speed Two all the way, will these destinations have a direct high speed classic-compatible service? There’s plenty of space capacity on High Speed Two.
  • I don’t think the Sheffield and St. Pancras services will be dropped, but they might be.
  • CrossCountry will probably be running intelligent multi-mode trains capable of 125 mph running and up to 140 mph in places.
  • Northern’s service between Sheffield and Nottingham might go via a reopened Barrow Hill Line.

But the biggest change will be that these two fast lines will be to High Speed Two standards.

  • Sheffield and Chesterfield will be electrified.
  • There will in-cab digital signalling, which theoretically could probably allow eighteen tph on the route.
  • High Speed Two Trains between Sheffield and Chesterfield will take twelve minutes.
  • Sheffield station will have been modified as required, to be able to handle all trains very efficiently.

But it would still be carrying a modest eight tph.

If required Sheffield would have the capacity to accept more trains from the South.

I wouldn’t be surprised to see, the following trains added.

  • An extra tph to and from London Euston via High Speed Two.
  • Two tph to and from Birmingham Curzon Street via High Speed Two.

I also wouldn’t be surprised to see CrossCountry using classic-compatible High Speed Two trains and switching to High Speed Two between Birmingham New Street and Sheffield. But these trains would still use the same tracks to access Sheffield station.

But I am led to the conclusion, that Sheffield will have more than enough capacity linking the City to Chesterfield and the South.

Future Services On The Slow Lines

Or should I use lines connecting to the Hope Valley Line rather than slow lines?

Currently, the following services take the slow lines between Sheffield and  Dore & Totley stations.

  • East Midlands Railway – Liverpool Lime Street and Sheffield – via Manchester Piccadilly – 1 tph
  • TransPennine Express – Manchester Airport and Cleethorpes via Manchester Piccadilly – 1 tph
  • Northern – Sheffield and Manchester Piccadilly – 1 tph

 

Transport for the North aims to run a four tph service with a forty minute journey time between Manchester Piccadilly and Sheffield.

Consider.

  • 100 mph TransPennine Express trains take fifty-three minutes between Sheffield and Manchester Piccadilly without a stop.
  • Classic-compatible trains with a battery capability could easily handle the route.
  • Northern’s services on the Hope Valley Line are timed for 75 mph trains.
  • Dore & Totley and Hazel Grove stations are twenty-nine miles apart.

If between Dore & Totley and Sheffield stations were to be electrified and track improvements like passing loops were to be made to the Hope Valley Line, I believe that to achieve a forty minute all-stops timing between Sheffield and Manchester Piccadilly, would need a train with the following specification.

  • Electric train with batteries.
  • Four cars
  • 100 mph or faster operating speed.
  • Step-free access between platform and train.
  • Sparkling acceleration and deceleration.
  • Ability to run under in-cab digital signalling to keep out of the way of freight services.

Looking at Crossrail between London Paddington and Maidenhead stations, the London route is probably as difficult as the Hope Valley Line and it has been designed as a forty minute service with ten stops, using a modern electric train.

If TransPennine fitted batteries to their Class 802 trains, these trains would fit the Northern Powerhouse Rail requirements.

East Midlands Railway and Northern would find that the following trains could be used.

  • Bombardier – Aventra with batteries
  • Bombardier – Class 377 train with batteries
  • Bombardier – Class 379 train with batteries
  • CAF – Class 331 train with batteries
  • Hitachi – Class 385 train with batteries
  • Porterbrook – Battery/FLEX train based on Class 350 train
  • Stadler – Flirt with batteries

All would need that between Dore & Totley and Sheffield stations be electrified.

After the upgrades and the new or refurbished trains are running, this would mean that between Dean & Totley and Sheffield would be handling four tph, which would be semi-fast trains between Sheffield and Manchester Piccadilly. Although to current passengers on the line, they would seem to be fast services of a much higher standard.

It would not be very different to how the slow lines into Paddington also handle about four tph of other services, including GWR services and freight.

I believe that to provide an adequate service to the reopened and rebuilt stations of Dore & Totley, Beauchief, Millhouses & Eccleshall and Heeley, that a Turn-Up-And-Go service of at least four tph should be run between Dore & Totley and Sheffield stations.

A Turnback At Dore & Totley

This Google Map shows Dore & Totley station and the area to the South.

Note.

  1. There would appear to be a lot of space between the Midland Main Line and the single track, that leads between Dore & Totley station and the Hope Valley Line.
  2. Flying my helicopter, as low as I dare, it looks like the area is either a rubbish dump or very low grade businesses.
  3. Crossrail has designed turnbacks at Abbey Wood and Paddington stations, that will handle twelve tph.

I believe that it would be possible to design a turnback at Dore & Totley station, that would handle eight trains per hour, if not twelve tph.

It might even be possible to squeeze in some overnight stabling.

Trains Or Tram-Trains Between Dore & Totley And Sheffield Stations

In my view, it doesn’t matter.

Crossrail’s 12 tph turnbacks can handle a 205 metre long Class 345 train, so I’m sure a well-designed turnback at Dore & Totley could handle a mixture of any trams or tram-trains below a defined maximum length of say 140 metres, which would be defined by a pair of Class 185 trains, which might have to be turned back during service disruption.

Where Would The Services Terminate in The East?

It is my view that cross-city services like Birmingham’s Cross-City Line, Liverpool’s Northern Line, London’s Crossrail and Thameslink, Newcastle’s Metro and Paris’s RER are efficient for both passengers and train operators.

So Dore & Totley station could be one end of a Sheffield cross-city line, with a frequency of at least eight tph through Beauchief, Millhouses & Eccleshall, Heeley and Sheffield stations.

So where would services go on the other side of Sheffield? Wikipedia gives these as services to the East of Sheffield.

  • Leeds via Barnsley and Wakefield (fast) – 2 tph
  • Leeds via Meadowhall, Barnsley, Wakefield and Castleford (stopping). – 1 tph
  • Leeds via Meadowhall, Moorthorpe and Wakefield. – 1 tph
  • Scarborough via Meadowhall, Doncaster, Hull and Bridlington. – 1 tph
  • Lincoln Central via Worksop and Retford – 1 tph
  • Gainsborough Central via Worksop, three trains per week continue to Cleethorpes via Brigg. – 1 tph
  • Huddersfield via Meadowhall, Barnsley and Penistone – 1 tph
  • Doncaster via Meadowhall and Rotherham, with one train per hour continuing to Adwick – 2 tph
  • York via Moorthorpe and Sherburn-in-Elmet. – 3 trains per day (tpd)

For much of the day, that is a frequency of 10 tph, with 5 tph calling at Meadowhall, 2 tph calling at Worksop and two fast tph passing Meadowhall without stopping.

But there are other rail projects under development.

I can see classic-compatible High Speed Two trains serving the following places to the East of Sheffield.

  • Leeds
  • Hull via Doncaster
  • Scarborough via York
  • Cleethorpes via Doncaster, Scunthorpe and Grimsby.

A train like a five-car Class 802 train would probably be enough for most routes except Leeds.

I can see the following terminals for tram-trains to the East of Sheffield.

  • Doncaster and Doncaster-Sheffield Airport
  • Waverley station, which could be on a loop from the Sheffield and Lincoln Line.
  • Barnsley Dearne Valley

There may well be others.

If Sheffield were Karlsruhe in Germany, the tram-trains would probably serve the following routes.

  • Huddersfield via Penistone.
  • Lincoln via Worksop and Gainsborough.
  • Manchester via the Hope Valley Line.

But the Germans have a much larger electrified core, than Sheffield will have, even if High Speed Two electrifies between Dore & Totley and Thurnscoe stations via Sheffield.

I can make a table of destinations and distances and how they could be served.

  • Barnsley – 16 miles – Possible return trip from Sheffield for a battery electric train.
  • Barnsley Dearne Valley – 8 miles from Rotherham Parkgate – Possible return trip from Sheffield via Rotherham Parkgate for a battery electric tram-train.
  • Doncaster – 11 miles from Rotherham Parkgate – Possible return trip from Sheffield via Rotherham Parkgate for a battery electric tram-train.
  • Chesterfield via Barrow Hill – 17 miles – Possible return trip from Sheffield for a battery electric tram-train.
  • Doncaster Sheffield Airport – 10 miles from Doncaster – Possible return trip from Sheffield via Rotherham Parkgate and Doncaster for a battery electric tram-train.
  • Gainsborough Lea Road. – 32 miles – See Lincoln Central.
  • Huddersfield – 36 miles – Possible battery electric train with charging at Huddersfield.
  • Hull – 59 miles – Possible battery electric train with charging at Doncaster and Hull.
  • Lincoln Central – 48 miles – Possible battery electric train with charging at Lincoln and/or Gainsborough Lea Road. Otherwise diesel.
  • Penistone – 23 miles – Possible return trip from Sheffield for a battery electric train, using Newton’s friend on the way back.
  • Retford – 23 miles – Possible return trip from Sheffield for a battery electric train.
  • Waverley – About 6 miles – Possible return trip from Sheffield for a battery electric tram-train.
  • Worksop – 16 miles – Possible return trip from Sheffield for a battery electric train.

It looks to me like a mix of battery electric trains and tram-trains could run most of the services from Sheffield, if services that used new High Speed Two infrastructure used classic-compatible trains or trains like the existing Class 802 trains, that have been converted to battery electric operation.

Note.

  1. I am assuming, that a battery electric train has  a range of 56 miles on a single charge.
  2. Rotherham Parkgate station is changed to a through station.
  3. Tram-trains passing through Doncaster can recharge on the station’s 25 KVAC overhead electrification.
  4. Charging can be provided as required at other stations.

There are lots of possibilities.

Consider, this for tram-train extensions to Barnsley Dearne Valley, Doncaster and Doncaster Sheffield Airport.

  • Extend the tram-train service at Rotherham Parkgate to either Doncaster and Doncaster Airport or Barnsley Dearne Valley stations.
  • Run tram-trains between Dore & Totley and Rotherham Parkgate via Sheffield, Meadowhall and Rotherham Central.

This would give a double-ended route across Sheffield and Rotherham between Dore & Totley and the existing Supertram network in the West and Barnsley Dearne Valley, Doncaster and Doncaster Sheffield Airport in the East.

Consider how to connect the branch to Waverley station to the Supertram network.

  • Waverley station will be either on or on a loop from the Sheffield and Lincoln Line.
  • The Sheffield and Lincoln Line has no obvious connection with the Supertram network.
  • The Sheffield and Lincoln Line goes straight in to Sheffield station.
  • Trains to Lincoln always appear to use Platform 4 in Sheffield station.
  • Sheffield station has four through platforms.

This Google Map shows where the Sheffield and Lincoln Line passes behind the Supertram Depot at Nunnery.

Note.

  1. The Nunnery Square Park and Ride is in the South West corner of the map.
  2. The Supertram depot is to the East of the Park-and-Ride, with the Nunnery Square tram stop to the South.
  3. The Woodbourn Road tram stop is in the North East corner of the map.

This second Google Map shows the lines around the Park-and-Ride.

I suspect that a connection between the Supertram system and the Sheffield and Lincoln Line, could be built to the North of the Nunnery Depot.

But would it be easier to continue to Sheffield station or pass through the station and terminate at Dore & Totley station?

I can’t be sure looking at the maps, but it could be logical that trains to and from Lincoln use the Southern pair of tracks past the Nunnery Depot, as they would be on the right side of the tracks for Lincoln.

This would make it easier to do the following.

  • Create a connection between the Nunnery Depot and the Sheffield and Lincoln Line, which would surely be needed for efficient maintenance and operation of tram-trains running to and from Waverley.
  • Allow tram-trains used to serve the proposed Waverley station to return to the Depot every night.
  • Allow tram-trains working between Sheffield and Meadowhall to use the Lincoln and Sheffield Line to enter the Nunnery Depot.
  • Build a tram stop/station by the Park-and-Ride.

There would also be less need to build another depot.

Looking at the maps, could there be space to extend the Nunnery Depot?

Conclusion

This could be a very good project.

  • It fits in well with the plans and needs of High Speed Two.
  • It connects the new Waverley station to Sheffield station.
  • It fits well with the Sheffield Region Transport Plan 2019.
  • It connects Sheffield, Rotherham and Doncaster to Doncaster Sheffield Airport.
  • It opens up the Hope Valley Line to improve services between Manchester and Sheffield.

I also don’t think, there’s any great risk!

 

 

 

 

 

 

 

I

 

 

 

July 12, 2020 Posted by | Transport | , , , , , , , , , , , , , , , , , | 3 Comments

Ashington Blyth and Tyne Line Reopening Mulled Over In Six ‘Quick Win’ Rail Projects For Northern Transport

The title of this post is the same as that of this article on Rail Technology Magazine.

This is the first paragraph.

A series of ‘quick wins’ have been identified to fix the “current crisis” in the north’s transport network in a report by the IPPR.

What are the quick wins?

This page on the IPPR website gives access to the report which is entitled Quick Wins For The North’s Transport Network.

These quick wins are given in the report.

Reopening Of The Ashington, Blyth And Tyne Railway For Passenger Services

This summary is given.

North of Newcastle, and along the North East coast, there is an area with great potential but numerous challenges. This area contains several small and medium-sized towns: Blyth (population 37,000) and Ashington (population 28,000) are the largest (Centre for Towns 2017). The public sector dominates in terms of employment (education, health and public administration provide one-quarter of jobs), and the areas’ private sector is largely in the ‘everyday economy’ of retail (5,900 jobs) and food and beverage services (4,130 jobs) (ONS 2018c). The Port of Blyth handles 2 million tonnes of freight each year, and there are some significant development sites for renewable energy in the area (Port of Blyth 2018).

The history of the area is a vital consideration for its transport infrastructure. The area boomed during the industrial revolution as coal mining and port towns grew – Ashington was once considered the world’s largest coal-mining village (Whitfield 2018). The Ashington-Blyth and Tyne railway line once connected a number of Northumberland settlements between Ashington and Newcastle – it was not a single route, but a small network, built in 1840 to link the collieries to the River Tyne, and was opened up to passengers in 1841 (NCC 2015). But in 1964, passenger services were withdrawn under the ‘Beeching Axe’,although it has remained open for freight.

This idea has been talked about for years and I wrote about it in Northumberland Unveils £3.5m Rail Project To Bring Back Passenger Services.

This is a project, where it is probably time to stop talking and get the planning started, before updating the railways.

Surely, if it can be done for £3.5m, it must be good value. I suspect it will cost more, but not as much as Network Rail’s estimate of £191m.

Leeds/Bradford Airport Parkway Rail Station

Consider.

  • Leeds Bradford Airport handles four million passengers per year.
  • It has no direct rail access.
  • It has direct services to airports like New York.
  • It connects via hub airports like Heathrow and Schipol to a wide number of destinations.
  • It could capture more of the localo air passengers with better connections.

The proposal is to build a Parkway station the Harrogate Line, between Horsforth station and Bramhope Tunnel.

  • It would be a 1.3 kilometre drive in a shuttle bus to the Airport.
  • The station would serve as a Park-and-Ride station for Leeds, Harrogate and other destinations.

This Google Map shows the area.

Note.

  1. The Airport is in the North-West corner.
  2. Horsforth station is in the South-East corner.
  3. The Harrogate Line runs North South from Horsforth station.

The new Park-and-Ride station could be built on any convenient location near to the Airport.

It looks to be a simple plan, that has been costed at £23m.

Consider these points about the Harrogate Line.

  • It is only thirty-six miles.
  • Services take around seventy minutes between Leeds and York via Harrogate
  • It appears to be double-track
  • The operating speed is sixty mph between Leeds and Harrogate.
  • It doesn’t appear to be very busy.

I suspect it would be a good idea to iimprove this line, so that Northern’s Class 170 trains can stretch their legs.

If there was a Park-and-Ride station at Leeds Bradford Airport would First TransPennine want to run a service to the Airport?

I can see this plan, stimulating a lot of rail improvements between Leeds and York.

Supporting The Development Of Hydrogen Trains

The IPPR report says this.

Transport for the North plans to work toward the roll-out of hydrogen trains.

Consider.

  • The North has a lot of routes, where hydrogen-powered trains could be used.
  • Alstom are converting trains to hydrogen-power at Widnes in the North-West.
  • Hydrogen is or can be produced by petro-chemical companies in the North.

I feel that increasingly, the North will have another big problem, for which hydrogen could be a solution.

Currently, there is a massive expansion of offshore windpower, which will produce a lot of electricity at awkward and random times, when it won’t have an obvious use.

So it will need to be stored!

One sensible method energy storage is to use the electricity to electrolyse water or brine to produce hydrogen and other gases. The hydrogen is then stored and can be burnt or used in a fuel cell to generate heat and/or electricity.

I can see a lot of innovation being employed to create hydrogen filling stations for users, such as companies with large fleets of smaller vehicles, railway companies, emergency power sup lies and other applications.

Unlike the production of hydrogen using steam-reforming of methane, electrolysis using renewable energy doesn’t produce any carbon dioxide.

Tees Valley Rail Interventions

The report talks of these interventions.

  • Darlington station upgrade.
  • Middlesbrough station upgrade.
  • Teesport To Northallerton gauge clearance.

One of the main reasons for doing this, is that it will improve access to Teesport, which will bring wide benefits to the North.

Integration Of Traffic Management To Improve Air Quality

This is from the report.

Air quality is a major health problem across the world – especially in major cities. Vehicle emissions are the major contributor to this problem – particulate matter and nitrogen oxides cause numerous health problems, including asthma and lung cancer. Road transport accounts for at least 50 per cent of these emissions – and this is likely to be an underestimate (Cox and Goggins 2018). Clearly the volume of traffic is the principal cause, but so is the ‘stop/start’ of traffic flows, which tends to further increase emissions (O’Brien et al 2014). Exhaust fumes aren’t the only source – 60 per cent of particulate matter emissions come from the tyres and brakes.

Suggestions to reduce emissions include.

  • Freight priority schemes
  • Bus or cycle priority at signals to encourage transport modal change.
  • Change signal timings to improve air quality
  • Inform the public to change travel plans when air quality is poor.
  • Low emission zones

Some of these measures will go down like a lead balloon.

Tees Crossing

This is from the report.

Roads are essential for the internal operation of Tees Valley’s economy and in order to connect it to the wider North. Passenger rail connectivity remains poor and light rail is non-existent. The economy’s residential and employment centres are highly dispersed across its geography. A modern bus network might relieve pressure, but the deregulated and underfunded network has seen passenger numbers fall and services cut (Brown 2018). The level of freight activity in Teesport and Hartlepool mean that these ports are highly dependent on the road network as well as rail.

The proposed solution js to build another road bridge across the Tees.

Conclusion

It seems a package of sensible measures, but opposition to some may ean they are not implemented.

 

 

 

 

 

 

March 19, 2019 Posted by | Transport | , , , | Leave a comment