Skyways as Cycle lanes

While skyways evolved as a variant on PRT ( Personal Rapid Transit ) and elevated /monorail. It also needs to be thought of as a cycle lane. This section is a look at skyways as cycle lanes. The PRT ( Personal Rapid Transit ) theory holds sway as the skyway system is intended as a commuter theory. Different countries view cycling differently, US Data shows that only 9% of cycle trips are work related[ 1 ] quoting NPTS report, with the majority of trips being for recreation. In European countries the values are reverse with the main number of cycle journeys being for utilitarian reasons. The recreational focus explains why dedicated cycle routes are placed on an 'as available' basis preferably in park land in the US. For US readers the mind change to a utilitarian approach is a larger leap.

One survey done a long time ago, for which I have lost the reference too, ranked the reasons why people would not cycle to work as this

  1. Danger - Threat of collision with cars.
  2. Time - It would take longer to cycle than to drive.
  3. Exposure - Traveling by car keeps you warm/cool dry cycling does not, exposure also includes rain, wind, car pollution
  4. Effort - This is sometimes indicated by people saying 'I don't want arrive all sweaty', this is compared to almost zero personal energy in a car.
  5. Lack of facilities - ( parking, changing )

Lets look at these one by one comparing skyways to cycle ways

Danger

Around 800 cyclists are killed annually in the US, a further 500,00 are injured[ 1] . Most of the more serious injuries are caused by collisions with cars. The logic would suggest that a separate path would reduce these problems assuming an increase in traffic. This is a debated concept, most cycle paths are created on an 'as available' basis that is they are fitted in where space permits not because the demand exists. Some cyclists fear separated roads as they have had a long and historic struggle to remain 'road' users. The notion of a separate system historically reduces mobility rather than increases it. As such planning weight tends to be shifted towards cycle lanes - the same roads as cars but the space may be separated by a painted line. These have the advantage of making cyclists feel they are not being pushed off real roads. The also can be installed on the marginal width available and so can be selected to take advantage of the kinds of routes real riders really want. Painted lines are relatively cheap to 'install' - all you need is a plan and some paint. The down side is that they frequently become filled with cars using the lane as a parking space. There can also be a tendency to share cycle lanes with bus traffic - the detriment of both bus and bikes. Busses tend to stop regularly ( even when not at junctions) forcing riders to either turn out into traffic or pass on the inside endangering the passengers getting on and off the routes. Busses also tend to be slowed down from there top speed when cyclists are in the way.

Clearly the part of the reason that dedicated cycle routes are underused is that dedicated cycle paths don't go any where. By sticking to safer back routes they make navigation much harder. Where Cycle lanes have been more popular - they tend to follow the street system and actually have the advantage of going somewhere one might find useful.

Both dedicated cycle lanes and skyways do well until we reach a junction. As Gårder et al states states 'Urban bicycle paths can increase the risk of car-bike collisions at intersections to the point that overall risk can be greater than ordinary roads [ more info ]. One report ( Wachtel and Lewiston (1994) ' They found that bicyclists crossing intersections from sidewalk bike paths were 1.8 times more likely to collide with cars than were bicyclists crossing intersections while riding in the street.' ( see ) Jeffrey Hiles goes on to observe ' But when riding against the flow, road riders had twice the risk and sidewalk riders had four times the risk of those riding the same direction as the motor traffic on their side of the street' .

Cycle lane dangers Diagram after Jeffrey Hiles, Listening to Bike Lanes elevated cycle ways have non of these problems.

The skyway concept uses separate lanes. This decreases the potential shadowing of the street, means we reduce in tube head on collision accidents, introduce the possibility of using air streams to increase over all speeds, possibly slowly tilt the tubes for a regular 'down hill' motion and manage entry to and from the travelators for level change. This means we can also be quite cleaver about where to put the station/on ramp. For example the on ramp can be in the right direction between intersections so decreasing the potential problems when drivers encounter them for the first time.

Separated cycle lanes, feel safe but studies the can be less safe than cycling on the street! The problems occur at junctions. Skyway solution - get rid of the junctions.

 

Returning to danger, avoiding junctions naturally avoids junctions based accidents. The skyway system operates like an urban cycle freeway/parkway system, limited connections and no stops. Like an arterial it depends upon local feeder roads which for the time being are likely to be bike lanes or ordinary streets. There will be a rise in potential danger when you leave your skyway system and join the street grid again. You do have the choice of walking on the sidewalk with your bike. If a cyclist wishes to continue on the road then hopefully the existence of a skyway network and its station will alert drivers to the potential existence of cyclists. By making cyclists a common appearance on the roads, the car driving public will come more familiar to sharing the road as they do in cities such as Amsterdam( Holland ) and Cambridge ( England). A successful skyway would drive up the numbers of cyclists in an urban center so hopefully providing a reason to introduce more facilities. The skyway system would reduce journey time and the 'stations'/off ramps would become natural centers for a network of street cycle lanes reaching out to the surrounding urban fabric.

The position of the 'stations'/off ramps, could in some circumstances reduce danger by being in the immediate vicinity of a particular building. A station could placed in relationship to a school so that children do not have to cross the road to reach the grounds of the building. A station right next ( but not in ) a school, could offer children the same kinds of transportation benefits that skyway commuters would. The CDC has identified obesity as a primary threat to American health and a problem which is on the increase. Children could be supervised individually as they cycle to school. Groups could travel on a crocodile with a small number of responsible adults. Once seen to an on station, intelligent older children could travel by them selves safely away from both pollution and the dangers of traffic. The skyway system contains a network of security cameras, and security officers which would be a reassurance to parents that there children would be completely safe until they emerged from the skyway at school. This is not the place to labor the reasoning the benefits of giving children a space and a time where they can be both in charge of there own day and obtain quantities of regular exercise. It seems important to have as a baseline for the design of the skyway system the question - 'Would I let my children ride of this'.

At some point larger organizations may create direct entrances to the skyway level to their building, much in the same way certain buildings link directly to rail stations, or have the lower floors dedicated to parking. Unlike overhead rail or monorail, the skyway system would transmit little or no,load, noise and vibration into the main building. A direct connection to a building would mean zero exposure to the main urban road network for the commuting cyclist.

At night the skyway system would be light until it was closed. By keeping the cycle way well light and separate from the road network it would be possible to keep up high speeds with little danger. The ability to see long distances without needing powerful lights would enhance the safety of the skyway system.

So far we have been looking at how the elevated cycle way system might solve problems of the perception of danger. This section move on to look at some of the unanticipated dangers. One excellent review [ here] by John Franklin's of Milton Keyens Redways- separate cycle lanes. Show that these separate routes are more dangerous than typical routes even cycle lanes on the road. To quote John Franklin the reason for the these accidents where 'Poor visibility (particularly at junctions) is the biggest single cause of accidents, but other common causes include sharp bends, steep gradients, bollards, slippery bridges, loose gravel and mud. In short, features which are not compatible with the inherent limitations of a bicycle. The paths are often not suitable for typical cycling speeds. Some very serious injuries on Redways have been as a result of head-on crashes between cyclists, collisions with dogs, and eye injuries from intruding vegetation, all of which are rarely encountered on roads.'

Unlike a Redway or traditional separate cycle path , the skyway has no sharp curves, no vegetation, no straying pedestrians. By remaining on the level we avoid the necessity of gaining momentum to handle going down then up again. The speeds near the bottom of the 'dip' can be quite high, poor surface, loose gravel and lead to a bad injury. The skyway the surfaces are dry and isolated from the weather. The movement system is strongly regulated in to one lane direction so there are no head on collisions. The lighting and surface would have to be maintained, mostly there are no gradients, no bollards, no dogs and no obstructions. If a toll is charged then it will be useful to maintain the network - policing vandals,dogs and pedestrians, identifying roof leaks and keeping the riding surface clear.

Notice that the skyway system is never going to eliminate the necessity for on road movement, indeed it is quite dependent on the feeder networks. Does a elevated cycle network imply more on road accidents, not necessarily, Charles Komanoff suggests in a letter to Injury Prevention magazine, that there is an effect of 'safety in numbers' he claims ' the probability that a motorist will strike an individual cyclist on a particular road declines with the 0.6 power of the number of cyclists on that road.' Following this logic an increase in cyclists encouraged to use the road network by the elevated cycle way will help to reduce the average risk. The more successful the network the more car drivers will be aware of cyclists the less accidents will occur. By careful positioning of cycle lanes we can reduce the junction related problems. In town by combining stations with bike storage, showers and change facilities we could encourage cyclists to walk from the stations if safety became an issue. A reasonable large scale experimental system has to be introduced to help understand the problem. Hopefully a case of success breading success, more bikes emerging from stations the more car drivers become relax about on the road cyclists so reducing rates of accidents. As more cyclists emerge from long periods safely segregated from the road network the demand for cycle lanes and cycle paths emerge to further increase security. Perhaps one day as buildings are designed near cycle routes they might include elevated entrances the way they currently include internal car parking reducing to zero the need to emerge on the street in the city center.

 

Time

As mentioned in a number of other locations here, the thinking behind the elevated cycle way concept is that behind the PRT Personal Rapid Transit scheme. Why does a PRT system save time over a normal bus, light rail or monorail ? It saves time due to eliminating the need to change at stations and more importantly the need to stop a junctions. Assuming an average speed of 13.3 miles per hour[why] then for much in town traffic this matches or exceeds the speed of the local traffic if you include the waiting at stops. The problem with a bike is that it must also stop at the same lights. The overhead concept removes the necessity for stopping at junctions, by having east west lines above north south lines there is no reason to bump into another so this would even be faster than if you managed to remove all cars and had a cycle only city. By flattening out the route ( no hill climbing ) by possibly managing flow by pushing air though the system then it should be possible to make the 13.3 mph speed the average speed. For journeys which are less than 3 miles (48% of the trips in the US are less than 3 miles ) this equates to 13.5 minuets at the average speed of 13.3 mph. Which could well be less for a number of travelers than driving. Traditional cycle lanes don't offer the concept of time reduction, the bikes have to slow and stop then pull away again. This can increase energy consumption by 400%. By being elevated the elevated cycle way does not have the same restrictions on placement as a traditional cycle lane. Both these factors if used well would put the cycle lane on the space which would reduce journey distances for the majority of cyclists. At best Cycle lanes are currently placed where they fit with little regard to what would be most effective as a commuting arterial, at worst they are regarded as a leisure amenity and as such become far to circuitous 'weaving' though a land landscape they should be cutting though. As mentioned later this weaving and the typical landscaping of a leisure route are strong contributing factors to the danger of strongly segregated cycle routes. Naturally good planning has to happened for the cycle way to achieve the kinds of time efficiencies needed. Thinking of cycle way as PRT means we can reuse the kinds of planning tools developed for PRT to help layout the network and minimize time.

One natural speed advantage of a raised cycle network over a at gradient network is the natural elimination of a number of blockages which are common on cycle lanes. These include parked cars, pedestrians, dogs, organic debris( trees), organic blockages ( sharp bushes invading the path), refuse bins, broken bottles and cans. While it's impossible to imaging a completely refuse free system ( even with frequent sweeps by the maintenance crew keeping the surface in pristine condition ) it is possible to reduce them to a minimum. By providing direct lighting it is also possible to facilitate fast journeys in conditions where the at grade conditions might cause the cyclist to slow down due to lack of light.

The enclosed nature of the cycle network also removes the effect of strong head winds. As mentioned else where the energy to overcome wind resistance grows with the square of the relative velocity. The result of this is that wind can cause a sharp drop in velocity. The skyway concept eliminates strong winds and in more extreme measures generate artificial winds to your back. This is something which cannot be matched by an at grade cycle path.

You might be wondering why the continued emphasis though out the site, on reducing the travel time for the average commuter. This is in large part due to the why traffic models work - there is a tendency in traffic planning communities to assume that if people have a choice of alternative modes of transport - car, public transport, walk. That the largest share of mode choice will be by the mode of transport which takes least amount of time. Traffic modeling dominates the choices for how funds are allocated in an urban context. As such if we expect a real investment to come ( from any source ) it will have to fit into to the less time is more riders view of traffic modeling. Cycle lanes have other advantages ( pollution, personal health, equal accessible and so on ), which tend to be rightly emphasized over journey time. Skyways has the conceivable role of making door to door journey time ( over peek velocity) a potential allies of the cycle proponent.

By eliminating junction stops, hills, interruptions, wind the elevated skyway should match the average speed to the natural moving speed of the bike. This is something which just can't be matched for the cost by a at grade cycle way.

Exposure

On a beautiful sunny day cycling can be a pleasure, In a park you can hear, the slightest sound forest. A pleasant day thousands are drawn to the many recreational cycle trails though out America. In the winter cycling is a slim distance from self abuse, you get cold, you get wet when it rains. In the height of summer in warmer climates, without shade the simplest walk to your can leave you damp with sweat. In the autumn wind can make the simplest journey on a bike a long labor in a low gear. It seems unreasonable to expect anyone to cycle in the pouring rain yet there have never been any expectations to 'cover' a cycle way. The separate nature of the skyway system implies that it is perfectly feasible to semi enclose the track.

A roof would protect against the rain and the worst stun. Lights in the roof would provide lighting This would also stop people trying to kill them selves by climbing to the top of the sides of the track. The walls would provide a view but be blocked off to the excesses of wind and rain. While careful attention would have to be paid to ventilation it would be possible to provide an wind/rain/snow/ free environmental for all of the year. Unlike a large scale system of cycle lanes, we would not get people returning to their cars and creating congestion on rainy days. Given that its unlikely you will live near a station there will be exposure to some of the elements on the way to the station. This is identical to the public transport rider except the use of the bike to get to the station reduces the time to get to the station ( and so exposure to the weather).

Naturally it's not impossible to have enclosed or semi enclosed ground cycle ways ( or skyways without legs ). How ever there is no clear example of this being suggested before. An Enclosed ground system might prove useful when taking advantage of narrow routes near rail or highway lanes. Enclosed cycle lanes would keep the traffic away from the people and the people away from the traffic, it might be possible to use a space which would be too narrow for a new car lane to provide a connection with practically no costs for rights to space. An enclosed lane would be sure to keep the potential for accidents between cyclists and high speed traffic to a minimum.

For very potentially very hot locations, Houston in Texas for example , there is nothing which forbids air conditioning the air entering into the skyway. The energy cost would unlike most of the rest of the skyways costs be a non capital cost. This implies there would have to be some on running funding to bear the maintenance and energy cost of the air conditioning. If the skyway is permitted to fund its self with tolls, it might be possible to cover the running of a cooled skyway system with out being a burned on the public purse. Without a working system, there is a minor question about the attractiveness of an uncooled/heated skyway. Any cyclist will tell you as you cycle your movement though the air provides cooling. In winter the exercise will tend to heat you up. The skyway system needs a period of experimentation to get all the details right - what about the questions of frost or condensation ? Once they have been solved the module can be reproduced on mass.

The skyway system removes the objections of exposure, you don't have to get wet,or push against the wind - unless you want to.

On a beautiful sunny day cycling can be a pleasure, In a park you can hear, the slightest sound forest. A pleasant day thousands are drawn to the many recreational cycle trails though out America. In the winter cycling is a slim distance from self abuse, you get cold, you get wet when it rains. In the height of summer in warmer climates, without shade, the shortest walk to your can leave you damp with sweat. In the autumn wind can make the simplest journey on a bike a long labor in a low gear. It seems unreasonable to expect anyone to cycle in the pouring rain yet there have never been any expectations to 'cover' a cycle way. The separate nature of the skyway system implies that it is perfectly feasible to semi enclose the track.

A roof would protect against the rain and the worst stun. Lights in the roof would provide lighting This would also stop people trying to kill them selves by climbing to the top of the sides of the track. The walls would provide a view but be blocked off to the excesses of wind and rain. While careful attention would have to be paid to ventilation it would be possible to provide an wind/rain/snow/ free environmental for all of the year. Unlike a large scale system of cycle lanes, we would not get people returning to their cars and creating congestion on rainy days. Given that its unlikely you will live near a station there will be exposure to some of the elements on the way to the station. This is identical to the public transport rider except the use of the bike to get to the station reduces the time to get to the station ( and so exposure to the weather).

Naturally it's not impossible to have enclosed or semi enclosed ground cycle ways ( or skyways without legs ). How ever there is no clear example of this being suggested before. An Enclosed ground system might prove useful when taking advantage of narrow routes near rail or highway lanes. Enclosed cycle lanes would keep the traffic away from the people and the people away from the traffic, it might be possible to use a space which would be too narrow for a new car lane to provide a connection with practically no costs for rights to space. An enclosed lane would be sure to keep the potential for accidents between cyclists and high speed traffic to a minimum.

For very potentially very hot locations, Houston in Texas for example , there is nothing which forbids air conditioning the air entering into the skyway. The energy cost would unlike most of the rest of the skyways costs be a non capital cost. This implies there would have to be some on running funding to bear the maintenance and energy cost of the air conditioning. If the skyway is permitted to fund its self with tolls, it might be possible to cover the running of a cooled skyway system with out being a burned on the public purse. Without a working system, there is a minor question about the attractiveness of an uncooled/heated skyway. Any cyclist will tell you as you cycle your movement though the air provides cooling. In winter the exercise will tend to heat you up. The skyway system needs a period of experimentation to get all the details right - what about the questions of frost or condensation ? Once they have been solved the module can be reproduced on mass.

The skyway system removes the objections of exposure, you don't have to get wet,or push against the wind - unless you want to. In case you are wondering about the utility of a semi enclosed cycle network. as your self this. If you where building a new bus route for commuters would you choose buses with no roofs ? If your where building light rail for commuters would you select open top light rail carriages ? If you where building a monorail would you have an open top monorail ? Why then if you are designing a cycle way for commuters do you insist on open top cycle lanes ?

 

Effort and Exertion

Less acknowledge and well below danger in the cycle aversion stakes, lies effort. This should not be underestimated. The observation that the flatter cites tend to have more cycling that the more mountainous cities should not be lightly dismissed. The success of rails to tails, the love of cycling along canals, all suggest people want to ride on the flat. The perception is equally important "Although walking and bicycling can be accomplished at low levels of exertion, some people perceive that these activities are beyond their capabilities Locational constraints such as lack of alternatives to high-speed, high motor vehicle volume roadways". ( BICYCLING AND WALKING IN THE UNITED STATES TODAY from FHWA COURSE ON BICYCLE AND PEDESTRIAN TRANSPORTATION.

Gradients especially steep ones are a hindrance for three further reasons, firstly they greatly decrease travel time and secondly they increase the perceptual distance, thirdly a down hill up hill event also makes cyclists want to free wheel down hill and use the gained momentum to assist up hill. The kinds of high velocities gained tend to make the cyclist a danger to the urban environment.

hills

Hills - Dangerous on the way down and hard work on the way up. Skyways remove them.

As mentioned else where, with a skyway system the local hills are removed by keeping the skyway 'flat' while using elevators and escalators to make sure the track is reached from ground level. Where changes in gradient are unavoidable the skyway can keep the actual experienced gradient to a minimum. That is from a long way away the skyway can being to slowly rise the gradient. Spreading the distance an given height has to be raised over a longer distance reduces the level of effort necessary to do this. This kind of cut and fill operation is common to monorails and overhead rail, and to rail it's self. Skyways can also use sloped travelators to lift the cyclists up a level, without slowing the cyclists down. Finally elevators should not be ruled out for some locations, where capacity is not a problem.

For a cyclist the nature of the ground is important to the maximum speed they are likely to attain. A cycle way would be a dry environment, it would never normally get wet, as such the best possible surface to reduce rolling friction could be used. The surface would be swept regularly to make sure the road would be free off broken glass and debris. This would permit cyclist to use high pressure (low friction) tires.This is a minor fact but it does contribute to the overall reduction of effort.

To minimize street shadow and visual interference, it is likely that skyway modules would be one way, one tube for north and one tube for south.This helps reduce two way accidents and simplifies junctions. It might be conceivable to reverse the gradient. That is tilt one skyway so it is higher near the beginning and lower towards the end. The stations to the skyway system are raised and naturally provide some mechanism to get on( elevator, escalator or ski lift). It might be possible given local geography to produce a skyway system with a consistent down hill design. As such we can further reduce the levels of effort required to the cyclist. It is unlikely that we will ever be able to produce a strong gradient to significantly increase the average speed but it might be possible in some cases to gently 'assist' the passenger though the system.

There have also been suggestions that fans might be used to push air from behind down the e skyway system. This again assumes a unidirectional tube. The friction caused by wind resistance grows by the square of the velocity, so if you require 10 watts of power to travel at 10 miles per hour you require 100 watts of power to travel at 20 miles per hour. By using a train to push the air 'out of the way', it was possible for Charles M. 'Mile-a-Minute' Murphy in 1899 to cycle at 57 miles per hour. By cycling directly behind a train he was able to use a shield to eliminate air pressure, basically the air about him traveled at the same speed he was.

Uniquely using the enclosed nature of the skyway, by using fans to push air down the tube it is possible to give a constant 'wind behind your back'. Less effort is needed to push against the rolling friction of the road so permitting the cyclist to theoretically reach a new higher speed with out much effort. The evaluation of speed increase against energy in electricity to drive the fans needs to be explored in order to find out what the maximum speeds could be achieved and what financial cost it would be to do active it. Designs would have to be evaluated to reduce noise from the fans and movement of air down the tube. For more on wind assist see the section on 'super skyways'.

The basic flat skyway system would reduce the effort necessary to travel though the system. More importantly it removes the perception of effort which explains the success of 'cycle to work days' Again, this is about giving choices. A slow personal speed would reduce the effort to move around the cycle way, the passenger has a choice about choosing a higher speed turn the skyway into there own personal gym.

Facilities

Further down the list of reasons and insignificantly against the danger factor is the presence of facilities. This includes the presence of something to lock the bike up against. and the presence of facilities to change from cycling gear to normal day way. This is a role the skyway stations could provide for. There could be locations to store bikes and provide facilities to change or have a shower. One argument against this it that the time taking to shower /change/ lockup and walk to work and will be attributed to the door to door journey time of the skyway. A test installation should provide enough information to estimate how strong the perceived dwell effect it might be.

Perhaps the argument is not that not enough people ride because there are no facilities but that the demand for the facilities will appear until number of cyclist increases.

So unlike ground cycle ways overhead cycle ways provide a number of unique advantages, over the traditional cycle way. Removing the danger is the most important, when people feel they are not going to die using the cycle system then the numbers of cyclist will increase.


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Side bar on fully faired recumbent

So far the discussion on Safety, Time, Exposure could also be matched by another technology. The fully faired recumbent bike [ example or here , or Human powered vehicles here ]. These kinds of bikes are enclosed by some semi ridged shell. This shell serves as both protective cover , aerodynamic assist and provision of some protection in collision. Theoretically these should meet some of the reasons why people don't cycle. In practice how ever, the addition of the faring increases the weight. For in town commuting on a normal road,cycle lane or cycle way then perhaps the necessity to stop and start at traffic lights, and the existence of hills makes the increase in energy necessary to lift the extra weight of the faring exceed that of the gains in energy when moving at speed. This all inherently assumes the stop/go/stop/go patterns of movement inherent in sharing the road with traffic lights and cars at every junction. Fully faired recumbent vehicles might gain from the uninterrupted elevated cycle ways.

 

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