Also of note:
the spike eastwards from Europe probably represents the Trans-Siberian Railway, with travel times increasing rapidly as one moves away from it.
Alaska is bisected by the Yukon River into two deep interiors.
Interesting map. I would, however, think that travel times in the middle of the Amazon basin would be much lower than shown. Even in 1914 a river steamer would probably have made it from Belem to Manaus in less than a week, and there would have been river boats on other major tributaries as well.
Likewise, there would have been river steamers on the Congo between Leopoldville (Kinshasa) and Stanleyville (Kisingani) that would have made travel considerably faster than indicated.
I missed this thread first time around, but I will share something potentially relevant. When I did my sailing trip several years ago we went from Nova Scotia to the Eastern Caribbean. It’s almost exactly due south. You might think we’d either sail a straight line, or follow the coastline to stop at ports along the way. We did neither; we sailed south-east for the first half of the journey, then turned to the south-west. I think we got far enough east to be in the same time zone as Greenland, although we didn’t bother changing the clocks.
I asked the first mate why we took that route. He said it had to do with the wind and the type of ship. The ship had mostly square-rig sails, and those work best going downwind; enough so that we took advantage of the west-to-east winds in the temperate latitudes, and the east-to-west trade winds as we got closer to the tropics. Apparently, the shortest route is not the fastest route.
Oddly, a multi-masted ship suffers a performance drop when it goes directly downwind. The wind will fill the sails on the aftmost mast, but the other masts (and their sails) are somewhat blocked. The best speed is several degrees off the wind, so that all the sails are capturing the wind. Combine that with the weather patterns around the world and finding sailing times would be very tricky indeed.
I can see how railways in India and Russia would result in the lowered travel times, but what would be responsible for that cone of yellow off of the western shore of the Americas out past Hawaii?
Remember, travel time is measured starting from London. Disembarking on the American east coast and taking a train to San Francisco, then proceeding from there. As I said earlier, why California is shorter trip than Chile.
ETA: the map actually shows the Central Pacific Railway terminating at San Francisco, and a southern line at San Diego.
The Panama Canal opened in 1914, which is the date on the map. It looks like the map is for the time before that happened, though.
One of my favourite bits of trivia -
If you are sailing from the Pacific to the Atlantic via the Panama canal, you travel West through the canal.