I was recently stuck in a traffic jam heading into the Lincoln Tunnel, travelling eastbound from NJ to NYC. When I was stopped for more than a minute or two, I shut off my engine. When the traffic started to move again, I discovered that I did not have to turn my engine back on because the incline of the road, in the last mile leading to the tunnel, is steep enough so that when I simply let off my brakes, my car began to move on its own. And, from a full stop, it accelerated quickly enough (and traffic was moving slowly enough) that I was able to keep up with the car in front of me (and even the notoriously impatient NYC-area drivers behind me did not honk at me). I continued this way, through stop-and-go traffic, for about 30 minutes, until I arrived at the toll gate. So, instead of moving slowly with my engine on, unnecessarily burning gasoline for half an hour, I was able to glide down the incline with my engine off.
It occurred to me that a significant amount of gasoline could be saved every day if, during rush hour, a lane were dedicated to drivers using this method. A quick search on the internet tells me that 120,000 cars use the Lincoln Tunnel every day. I suspect that the majority of these approach the tunnel during rush hour. If, for example, 10,000 drivers were to voluntarily use this designated lane and “glide” the last mile to the entrance with their engines off, this would save 1,200 gallons of gas. (This assumes a 30 minute delay, with the average car using one-eighth of a gallon of gas when idling for 30 minutes. I do not have real figures on the average delay at the tunnel but I often hear of delays of this length, or more, on the morning traffic report).
I also do not have any figures on the regularity of the time-of-day when these traffic jams occur. But whether they usually occur between 7 AM and 8 AM, for example, or if they occur more randomly or at other times, a sensor could be used to determine the speed of traffic. If the average speed is, for example, under five miles per hour, the sensor could light a sign above the start of the designated lane that would indicate that it is reserved for drivers using this gas-saving measure. (During other times, the lane would be available to all drivers).
There are two or three drawbacks with this concept but I believe they could be overcome. First, a car loses its power brakes when the engine is off. I had to exert a significant amount of force on the brake pedal to stop. But I was able to stop safely since I was moving so slowly, which would usually be the case when the traffic sensor activates the program. (In the event that traffic were to suddenly ease up after cars had entered this lane with the program in active mode, a speed limit of 10 mph could be in place to mitigate the braking issue. At a steady 10 mph, one would arrive at the entrance in no more than five minutes).
Also, a car loses its power steering when the engine is off. But this has a negligible effect at slow speeds. And there are gradual turns only when leading up to the tunnel entrance.
Finally, cars lose other electrical features when the engine is off, such as air conditioning and heating. So this may not be feasible in really hot or cold weather.
Even if this concept were to entail some inconvenience for drivers and even if it could not be used in inclement weather, I believe that a savings of several hundred gallons of gasoline (or more) a day, along with the resulting savings in pollution and greenhouse gases, would make it well worth the small sacrifices.
If you’ve read this far and you don’t think this is a crackpot idea, I have an extension of the concept: This could be used at other locations where drivers have to wait for significant amounts of time (if the entrance or exit is on a steep enough incline), such as drive-thru windows or parking lots. Further, perhaps future bridges, tunnels, parking lots, etc., could be engineered with such an incline at the entrance or exit, so that this concept could be put in place. Basically, this concept takes advantage of the cleanest and most readily-available energy resource on the planet: gravity.