In 2016 56% of Greater Brisbane travel to work was in a driver only vehicle. This suggests that short, narrow track (SNT) vehicles designed to carry only one or two people have the potential to reduce commute parking space requirements, congestion and transport energy consumption. (Short means short enough to angle park in a road that requires parallel parking for normal cars. Narrow means one passenger wide vehicles narrow enough to safely travel two abreast in a normal traffic lane.)
This post looks at what the maximum size of an SNT vehicle could be while still satisfying the above requirements. It also attempts to quantify some of the potential benefits. It was concluded that:
- The maximum size would be about 1.1×2.4m. This should be long enough to carry at least two adults with the passenger(s) behind the driver.
- 1.1m width is more than the width required to fit one person. This suggests that minimum width would be determined by stability considerations. (Electric SNT’s should have low centres of gravity because the batteries would be under the floor and motors at wheel level. Some SNT proposals have also had tilting cabins.
- In the short term, when only a few SNT’s would be on the road, SNT vehicles will deliver dramatic reductions in parking space and garaging requirements and small increases in road capacity. In the longer term, road capacity would be increased as more and more SNT’s actually travel two abreast in a single lane. (More than doubled if all wide cars were replaced by SNT’s.)
Summary of calculation results:
Calculations that were made for this post aimed at determining maximum dimensions for SNT vehicles. The answer was that a SNT vehicle should be no more than 2.4m long and 1.1m wide in order to meet the above requirements. A vehicle this size should be able carry the equivalent of at least two people with the passenger sitting behind the driver.
It was also estimated that:
- 3.5 SNTs ( 2.4×1.1m) will fit angle parked into a standard parallel parking place
- Short vehicles will give a small increase in road capacity because the distance taken up by car and safe spacing are reduced. (Assuming safe car spacing in metres is same as for larger vehicles.)
- Narrow vehicles won’t make much difference in road capacity until enough narrow track cars and motor bikes are available to make riding two abreast common. (Capacity would be doubled by the time 100% of vehicles are travelling two abreast.)
- The single 4.0×7.6m garage that comes with our unit would fit 5x(2.4×1.1m) SNT’s with room for door opening. Rearranging the garages that go with our block of units would allow even more SNT’s to be garaged. (Think of the area required to manoeuvre a wide car into and out of garages.)
Standard Brisbane bus width=2.590m
Standard Qld traffic lane width ranges from 3.0 to 3.5m depending on expected traffic mix and speeds.
How wide can a narrow track car be for 3m wide lane?:
Lane width less bus width=400mm= distance between buses travelling on the same side of adjacent lanes.
Max width narrow track that can drive two abreast in a single 3 m lane with 400mm separation=1.5-0.4=1.1m. (Assumes same spacing requirement as that for buses. (Should actually be less than this since cars are much shorter and easier to manoeuvre than buses.) NOTE: Doesn’t have to be 1.1mwide to fit one person across. Stability issues may actually decide min width. Keep in mind that an e-car would have batteries under the floor and motors at wheel level. (Some narrow track proposals also have tilting cabins to help stability. Modern accident avoidance tech should also allow narrow track cars to drive more safely two abreast.)
How LONG can a narrow track short car be and still angle park on a normal road that uses parallel parking for normal sized cars?
A short car could be up to 2.4 m long and still fit across an Australian standard parallel parking space. (2.4×5.4m).
How SHORT can a SNT car be? (A Vespa scooter that is 1.725m long has room for a pillion passenger.).
How many narrow track cars could angle park in a standard parallel car space?
3.6 x 1.1 m wide vehicles (with an extra 40mm width ea. for opening doors on one side) would fit in a 5.4m long parking space. More could be fitted if the SNT was narrower and/or passenger could get out and shut the door before car is parked. (A 0.8m wide SNT could fit 4.5 SNT’s in a 5.4 m long space.
How much will SHORTER vehicles increase road capacity?
Consider replacing a long car (4.8 m long) with a 2.4m long short car: If the long car is travelling safely with a 3 car length space (14.4m) the car will require a road length of 19.2 m per car.
I we assume that a 2.4 m long car will need the same safe length IN METRES as the long car, the short car will take up a road length of 16.8m. (This gives a 12.5% increase in road capacity per large car replaced by a 2.4 m long short car.)
If the traffic is going so slow that one large car length is safe spacing, replacing the large car with a 2.4m long short car the result in a 25% increase in road capacity. Keep in mind that short cars could be shorter than 2.4m. 2.4m is simply the max size for angle parking in a standard parallel parking space.
How wide would a dedicated SNT/motor cycle lane be?
A dedicated SNT/motor cycle lane provides a low cost option for increasing road capacity. It is assumed that this lane would need to be 1.5m, half the width of a 3.0m standard lane. In some situations a 1.5m wide track may be able to follow routes where there is not enough room for standard 3.0 m lanes.
Garaging cars takes up a lot of space and adds to the cost of accommodation. For example, our garage in the two story apartment building where we live takes up about 30m2 of which about 10 m2 is used as a storage area. If all the garage+storage space was used to fit extra units, the number of apartments could be increased by 40%. It is worth noting that According to The Urban Development Institute of Australia’s 2018 State of the Land Report and other sources, the cost of land for buildings was $746 /m2 with buildings $1271/m2 = $2017 for land +buildings. This is a bit dicey for garages but it would be very easy for garage price to be more than the cost of a standard car garaged in high cost land areas.
People like using wide cars because wide cars provide:
- Protection form the weather. (unlike active transport. (Bike, scooter or walk.)
- More protection from accidents than bikes, scooters and motor bikes
- Leave when you want to leave. (Unlike public transport.)
- Usually provide a more direct or faster route to the destination than public transport..
- Have at least enough space to carry the weekly shopping.
However, wide cars in particular do come with a number of limitations compared to other transport options:
- Require a lot of road, parking and garaging space.
- Energy guzzlers.
- Driver unable to relax and wind down after work compared with using public transport.
- Provide no exercise. (Unlike push bikes and walking.)
Most of the above comments would apply to SNT’s
So what would I want to use when?
If I were still commuting to work in the Brisbane CBD now I would probably want to use an E-bike when the weather was fine. (Use the E option to get to work without getting hot and sweaty and peddle without the E to get my daily exercise on the way home.) I might also have used an e-scooter/high frequency public transport combination if I thought the bike ride was unsafe. A car of one sort would be attractive when the weather was bad. An SNT would be the preferred car because of parking and congestion considerations.
My wife, on the other hand worked on the other side of Brisbane. For this location, a car of some sort was the clear transport choice because it was too far to ride a bike and the public transport route involved going all the way into the CBD before going back out to where she worked. Some days she may have wanted something bigger than an SNT to carry stuff for the job.
Some people want to get rid of cars and survive using public and active transport. Fine for some people who live, work and recreate in the right places. However, many make journeys that make a car of some sort is the logical source.
We should be looking for ways of reducing the damage done by transport to people, the environment, communities and property. However, my take is that some form of car is a logical part of the mix. SNT cars driven by renewable energy offer one way of reducing the damage done by transport while retaining most of the advantages of current model cars.