How to prevent pollution caused by a taxi rank? Is there a solution to the 'edging forward' cost of cars in a queue?

Question

I am looking at ways in which a heavily polluting taxi rank near a train station could reduce its pollution footprint. My first thought was that the pollution was mostly down to idling and I am thinking of various ways to tackle idling by taxi drivers.

Another reason for the pollution, the reason for this question (and possibly a larger source of the pollution than idling) is the constant 'edging forward' caused when: as each taxi at the front of the queue leaves after collecting a passenger, all the taxis in the queue move forward by one space and then stop. Sometimes there is a queue of 30 taxis and each taxi may move forward and then stop 30 times for every single customer they collect.

This 'edging forward' behaviour encourages the taxis to keep their engines running at idle because there is less time spent stationary. It is also less efficient edging forward in this way than if all the taxis moved forward by a larger degree every time they did move.

I was wondering whether there are any specific solutions to prevent this 'edging forward' behaviour in a queue of cars that would apply to a taxi rank?

(of course any other areas, ferry terminals for example or manual toll booths may also benefit or provide a solution).

Answer 1

Have the taxis (*) fill two or more lanes (| |) leading to the station, with one ready to pick up the next passenger (:)) coming out.

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:)   *

Once that cab leaves, an attendant at the head of the lanes signals for the next taxi to move forward, ready for the next passenger.

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All other taxis are parked with engines off.

Once that lane is empty, it can fill up with new taxis, and those in the next lane over are called for new pickups.

For a busy airport/station, more lanes, longer lanes, and multiple spots for pickup could be arranged.

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Answer 2

A variant of the system suggested by @LShaver, would be to use the numbered ticket system sometimes found in supermarket deli counters. Each arriving taxi takes a sequentially numbered ticket (which could easily be electronic using an app of some kind), and parks up in a parking area.

When a passenger arrives, they press a button, and the next number is called, and the taxi with that number then pulls up to the pick up area to collect the passenger. The button-pushing could alternatively be done automatically by a sensor noting the previous taxi leaving, so that the passengers don't have to do anything, or wait.

E.g. A taxi arrives and gets ticket 31. They see that number 25 is displayed, so they know that there are 5 taxis ahead of them, and that taxi 25 is waiting at the pick up area. A passenger arrives, and 25 takes them and goes - 26 is displayed, and the taxi with that number goes up to the pick-up area.

In a busy area, you could have the same system for passengers - they too take a ticket, with the same number on it, so the passenger with ticket 23 gets the taxi with ticket 23...

Another variant could use a camera to read the licence number of each taxi as it enters the holding area, and use that instead of issuing a ticket.

Answer 3

This is mainly a legal problem, with technical aspects. The difficulty in any system will be modifying driver behaviour. You really need enforceable laws against unnecessary idling, where the law, not the driver, defined what's necessary. One way to do this is to only permit taxis that can't idle (electric or hybrid cars).

Otherwise however good your system, people will just sit stationary for longer at a time, idling just as much.

In a long thin taxi rank a simple system can work: the front car always moves to the head of the queue, but subsequent cars don't move forwards until they can move at least (2 or) 3 spots forwards. This means they sit 3 times as long in one spot, and start their engines 3 times less often if they do switch off. I've sometimes seen this behaviour emerge naturally, in ferry check-in queues, and so long as no one cuts in to the gap in the queue, it has the advantage that not every driver needs to understand for there to be some benefit*. Bollards between parallel queues would help, along with lots of signs, but in the case of taxi ranks you'd need an attendant with authority. Certainly in my experience taxi drivers are among the most like drivers to complain about the price of fuel while doing nothing to reduce the amount they use.

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*I'm always one of the first to adopt this approach so I look out for it: I drive very little but my only motor vehicle (a campervan; more than half its mileage is on trips where I'm sleeping in it) is rather thirsty at idle.

Answer 4

What you could do is have a specially marked box that has the space for say 7 cars and instructions as follows.

1. if box is completely clear drive forwards onto it.
2. if a space becomes available do not move forwads (unless space is completely clear or the box is filling up from empty)

1 - all 7 spaces are empty

🚕 🚕 🚕 🚕 🚕 🚕 🛑 _  _  _  _  _  _  _     🚇

2 - so the cars move forward until the box is full

🚕 🚕 🚕 🚕 🚕 🚕 🛑 🚕 🚕 🚕 🚕 🚕 🚕 🚕     🚇

3 - a car at the front leaves because a pickup place by the station becomes available. The cars behind the box stay where they are

🚕 🚕 🚕 🚕 🚕 🚕 🛑 _  🚕 🚕 🚕 🚕 🚕 🚕     🚇

4 - more cars leave the box to pick up passengers. The cars behind the box continue to stay where they are

🚕 🚕 🚕 🚕 🚕 🚕 🛑 _  _  _  🚕 🚕 🚕 🚕     🚇

5 - all spaces become empty again so we go back to step 1.

🚕 🚕 🚕 🚕 🚕 🚕 🛑 _  _  _  _  _  _  _     🚇

this would reduce the edging forward behaviour which is poor in terms of fuel economy and pollution. With reducing the eding forward behaviour it will also give the taxi drivers more of an opportunity to switch off their engines and idle less.

n.b. I did consider having a traffic light that could change every 2-3 minutes. The problem with this is that it will not respond to the amount of clients. For example if you had one passenger every 4 minutes, with a traffic light system, you would still get the edging forward behaviour and associated pollution costs. Also if a very busy train came in then it may not move forward quickly enough. Possibly this could work if you had a sensor linked to the traffic light that would identify how much space was available ahead and change colour in response.

n.b. 2 - you could automate this further by having a barrier for the stop sign, and a sensor at the beginning of the box for 7 cars. Once 7 cars are sensed to have passed through the box, we open the barrier and let another 7 fill up the space.

Answer 5

A fairly inexpensive and simple automated system could be this.

when sensor2 counts 7 cars pass into the pickup area the gate opens and 7 more cars pass through before the gate closes (counted by sensor1)

                                      |  🚕|    🚂
             gate                     |  🚕|   station
____________closed____________sensor2_|  ↗ |📍  and
🚕 🚕 🚕 🚕  ⛩️  - - - - - - - -🚕 ⁞ 🚕 🚕|🚶pickup
‾‾‾‾‾‾‾‾‾‾‾‾sensor1 ‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾|    | 🚶 area
                                      |  🚕| 🚶 🚂

7 cars are counted to have passed through sensor2, so the gate opens

            gate                      |    |    🚂
            open                      |  🚕|   station
_____________⛩️_______________sensor2_|    |📍  and
🚕 🚕 🚕 🚕 → → → → → - - - - - -  ⁞     🚕|🚶pickup
‾‾‾‾‾‾‾‾‾‾‾‾sensor1 ‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾|    | 🚶 area
                                      |  🚕| 🚶 🚂

as 7 more cars pass through the gate the gate closes

                                      |  🚕|    🚂
             gate                     |  🚕|   station
____________closed____________sensor2_|    |📍  and
🚕 🚕 🚕 🚕  ⛩️  - -🚕 🚕 🚕 🚕 🚕⁞  → → | 🚶pickup
‾‾‾‾‾‾‾‾‾‾‾‾sensor1 ‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾‾|    | 🚶 area
                                      |    | 🚶 🚂