Free Doctor Who: Transit by Ben Aaronovitch

not wacca, could get close to that.
    They picked up the tail on the other side of Van Der Voek Station, a dusty no-place where a low-cost housing project had been abandoned. Naran banged her on the shoulder and she looked round. Behind them a black wedge of shadow eclipsed the vanishing point. It didn't look solid enough to be a train; besides, no one ran trains on the P-95 and a board was faster in the abstract nonsense that passed for velocity in a tunnel. The shadow was gaining on them, or at least it was getting larger.
    Mariko downloaded a traffic update as they coasted through the next station. She scaled up through a mantra to get into the next gateway and flipped down her visor for a look. An implant would have been better, but subdermal accessories were passe, far too common amongst artisans and the great unwashed. Getting one would be a sign of commitment though. Perhaps a modified optic with a discreet little plug under the hairline. Something she could accidentally reveal at parties, that would cause a stir, might even start a trend. The traffic update showed nothing on this stretch of the P-95 but that didn't surprise Mariko; you needed a transponder to be marked and she didn't think the shadow behind her had one.
    Distance was impossible to judge in a tunnel but Mariko was sure that the shadow was gaming on them. She knew that some of the classier security firms like Ninja Mechanixs had trained free surfers, there were also rumours that the military had souped-up machines. Trains that could outpace anything in the system, with exclusion shielding so that if you and it emerged at the same time, it would be there and you'd be paintwork.
    Mariko risked another look. Free boarding relies on absolute self-control and already she could feel herself drifting off line, losing the complicated harmonics of the music.
    The shadow was almost upon them. Deep in its core Mariko thought she saw two red lights like staring eyes. It was time, she decided, to get real.
    As they came out of the next gateway Mariko shifted her weight to the left and bore down hard. Naran followed her lead and the board swerved across the friction field. They dismounted before it hit the platform barrier and flipped. Mariko caught it on the second turn.
    'Where are we?' asked Naran.
    Mariko looked around. It was another ghost station. Minimal life support kept the temperature just above freezing; their breaths steamed in the cold air. On one of the walls an unfinished STS sign had the station name on the centre plate.
    'Buchanan Station,' read Mariko.
    'Any connections?'
    'No.'
    'What now then?'
    A breeze rushed through the station, stirring the dust.
    'We get off the platform,' said Mariko.
    As they ran for the exit the breeze grew into a great rush of air. Clouds of dust whipped and spiralled around them as they dived through the archway into the short connecting corridors between the platforms.
    'That's no train,' wailed Naran.
    Mariko grabbed Naran's jacket and roughly pushed him ahead of her. Looking back she saw it come into the station The gateway was spiked open by a cone of blackness, two red lights planted either side of the needle-sharp nose. It reminded Mariko of something created on a kid's graphic program, a rough representation of a train made up of basic 3D shapes - a cylinder tipped by two cones. It looked hypothetical, imagined rather than engineered, with no surface detail on its glossy black skin. When it stopped Mariko noticed that its base was half a metre above the friction field.
    Vertical lines of bright yellow light appeared at regular intervals along the cylinder body, where the doors would be on a real train. Then with a hiss they split open.
    'Run,' screamed Mariko.
    There was an access ramp at right angles to the corridor leading up into the unfinished heart of the station. Mariko dropped the board as they went scrambling up the slope; it clattered on to the concrete before sliding down to the level ground. The ramp went