Theory:Doctor Who television discontinuity and plot holes/Gridlock


 * Why didn't the Macra fly up and kill any other people in cars not in the Fast Lane?
 * The Macra are giant crabs. They do not have wings and cannot fly.


 * If the Face of Boe truly is Jack Harkness, it does not make sense for him to die, since he is immortal.
 * Jack still ages, just at a much slower rate. Assuming no further time travel, he's now over 5 billion years old.


 * Jack gave the last of his energy to open the motorway. This last energy could have been the energy that was keeping him alive.


 * On several occasions in both Doctor Who and Torchwood, Jack "died" and did not immediately revive until some time later. We don't know for certain if Boe really died and could have revived later.


 * There is no guarantee that Jack was even telling the truth about his nickname. He could have learned by other means that the Doctor and friends were acquainted with the Face of Boe, and be playing an elaborate joke on them.


 * Jack isn't immortal. He is described as a "fixed point in time". He survives until he can pass his message to the Doctor.


 * Why would the automatic quarantine let people into the motorway, possibly letting the virus in, but not let them back out?
 * The quarantine was to separate the lower city and motorway from the upper city, not the lower city from the motorway.


 * Wouldn't any of the later entries to the motorway have noticed that nobody ever came out, or even try to get out through the entrance shafts?
 * As far as later entries knew, those who had gone before were on their way to get out, not join a continuous loop. They did not know that they would never get out.


 * People from the under city were aware no one came back after going to the motor way. But how could they possibly "know" that no one ever reached the upper city?


 * What happened to the Macra after the events of Gridlock?
 * When the motorway opened up, the gas keeping the Macra alive would have spread away and they would have died.


 * In New Earth, the Doctor said that New Earth is in the galaxy M87, which is a real galaxy in the Virgo cluster. It is half a million light years across and 60 million light years away. Yet here the Doctor says that New Earth is 50,000 light years from Earth. In 5 billion years the Milky Way and M87 ought to be millions of light years further apart, not closer together.
 * Perhaps the people of the year 5 billion have the ability to move solar systems and galaxies around.


 * It is possible that M87 had been renamed or reclassified since now.


 * If there is self-replicating fuel, then how can the three passengers to go in the fast lane rule be meant to save fuel?
 * Although fuel is self replicating, it does not mean that it replicates the same amount that it uses. Perhaps only one in one million tonnes of fuel used is lost.


 * How does the self-replicating fuel and recycling waste products work? The second law of Thermodynamics means that you need some external input to keep your fuel supply going for that long. Especially if all the cars are generating exhaust fumes and hence losing some of their fuel as part of the process of using it.
 * Perhaps the fumes are the external input.
 * The fumes are the output of the fuel combustion anyway. So it would not give enough energy to fuel the vehicles due to the second law of Thermodynamics.
 * We do not know how technology will have advanced 5 billion years in the future. We could have discovered a way around the laws of Physics.


 * If it takes 6 years to go 10 miles, why don't people just walk?
 * Everything is sealed off, so the motorway is the only way to get anywhere.


 * What did the carjackers mean when they talked about being "too poor" to have a third passenger?
 * Some people may pay others to live with them so they can get into the fast lane.


 * When the car turns off all its systems, including the engines, how does it stay floating?
 * By 5 billion they could have invented a material that naturally repels gravity.
 * How would the cars land?
 * There would be a system to cause it to become relative to gravity.


 * The anti-gravity system could be part of the motor-way, and the reason that the Face of Boe still needed to contribute his life force to sustain it.


 * If the undercity was sealed off, then why is there both sunlight and rain in the section that the Doctor and Martha arrive in?
 * It was most probably artificial - to create an undercity illusion of climate.
 * Couldn't the energy used for this artificial climate be used to open up the motorway/lower city?
 * Yes, but not easily if the two systems ran on isolated grids. People from under-city may have been able to organise something along those lines. But only if they knew it would be necessary, and then only if there were a way to learn that upper city was safe again.


 * And how can a virus possibly infect an entire planet in just seven minutes?
 * Novice Hame mentions that everybody tried the mood drug Bliss and a virus mutated inside the chemical, then became airborne. In this state it wouldn't take long for the virus to spread through ventilation systems, especially if the majority of the population was taking it.


 * How was Boe sustaining the motorway?
 * By giving up his life force using some technology we don't understand.