Some Observations About Stanford Campus Traffic

1. Traffic lights that are controlled by bumpers, rather than being staggered to allow unimpeded flow along the main road.

2. NIMBY-ism: town councils that respond positively to every neighborhood's desire to increase their comfort and property values by impeding traffic, thereby lowering every other person's comfort and the value of their homes. If you think about it, this game isn't even 0-sum, it's negative-sum, so on average our lives become harsher, even if there are a few winners.

3. Four-way stop signs, perhaps the most irrational concept of all, and the topic of this essay.

How We Got 4-way Stop Signs on Campus

However, we live in different times. Rents are so high that for students and staff not given on-campus housing, the only options are often to live so far away that they have to drive to campus each day. Stanford victimizes these people in several ways. They are forced either to pay an incredible fee to park near their offices, or to pay with a wasted half-hour per day to park so far away that they have to take a shuttle to their office. These costs are not figured in, BTW, when Stanford compares its salaries with those at local industry, where parking is generally free and convenient. And of course the existence of myriad 4-way stop signs assures that those driving to campus will suffer additionally, even though they have no choice but to drive.

The True Cost of the 4-way Stop Sign

1. Unnecessary stops waste gas.

2. Unnecessary stops add to pollution.

3. 4-way stop signs create confusion and increase the risk of accidents.

To begin, let's do a back-of-the-envelope calculation to see how much gas is wasted at 4-way stop signs on the Stanford campus. Here are my best guesses at the parameters of the problem; feel free to inform me if you have better estimates.

• There are 13 stop signs between my home and office. In a more rational design (see below), these would be replaced by 2 stop signs and a traffic light at Campus Drive and Palm Drive. Thus, I could save 10 stops per trip. I'm going to assume I am typical, even though those traveling on or off campus (mine is an intracampus trip) probably encounter more unnecessary stop signs.

• Each stop consumes 2 ounces of gasoline. I read this somewhere; I have no idea where. However, if you compare typical city and highway mileage ratings for automobiles, and if you remember that "city driving" is defined by the federal government to be an un-city-like 1.6 stops per mile, you should convince yourself that 2 ounces is about right.

• There are about 20,000 students and staff at Stanford. I shall assume that each makes one trip per day onto campus and one off of campus. Staff and students living off-campus will drive on in the morning and off in the evening; on-campus students will make a trip from where they live to somewhere else and back once a day. The fact that we don't work weekends means fewer on-off trips but probably more off-on trips during the weekend.

With these numbers, we can estimate the amount of gas wasted at 4-way stop signs each day. There are 40,000 trips per day, each with 10 unnecessary stops, for a total of 400,000 unnecessary stops per day. These stops use 800,000 ounces, or about 6000 gallons of gas per day. What does that number mean in practical terms?

1. At $1.30/gallon, that's almost $3,000,000 paid for wasted gasoline per year.

2. Assuming 35 gallons of gasoline obtained from a 42-gallon barrel of oil, that's 60,000 barrels per year we wouldn't have to import from some country that really doesn't have our best interests at heart.

3. Since the vast majority of the pollution due to burning hydrocarbons occurs when accelerating the engine, we are probably creating pollution on campus something like burning that 6,000 gallons/day in an open field.

4. And if the vague risk to our health due to increased polition were not enough, we can argue that unnecessary stops actually cost lives directly. Suppose each unnecessary stop wastes 15 seconds of your life. 400,000 such stops consume 6 million seconds per day. If you are lucky, you will live 3 billion seconds. That means campus stop signs waste a lifetime every year and a half.

Added Aug. 1, 2003: I found the following Analysis From the City of Winnipeg. It looks at first like it is advocating 4-way stop signs, but if you read to the end, you see that they outline the same sort of arguments against that I presented here. They also assert that a stop sign increases the yearly operating cost of a vehicle that crosses that intersection daily (presumably 730 stops/year) is $50. Even assuming that is Canadian dollars, their number is about 5 cents (US) per stop, considerably above my estimate. They may be including more than gas, e.g., wear-and-tear on the brakes, which must be replaced eventually.

The Dangers of 4-way Stop Signs

At a 2-way stop sign, the rule is simple. If the sign is against you, you are burdened to make sure nothing bad happens. You may proceed only if you are certain there are no cars in the other direction that could hit you. It's hard to make a mistake if you are paying attention.

At a 4-way stop sign, it's not so simple. The rule is that the car arriving first can proceed first. If two cars arrive at the same time, you must yield on your right. But what does it mean to "arrive at the same time"? What if one driver, on the left, thinks they arrived 0.01 second before the driver on the right, while the one on the right calls the arrival "simultaneous." Each thinks they have the right of way. To make things worse, what does "arrive" actually mean? Can you "arrive" before you actually stop? Is crossing or touching the stop line equivalent to "arriving"? All this confusion draws the drivers' attention away from other matters, such as a bike or pedestrian trying to cross at the same time. The bottom line is that 4-way stop signs are an invitation to commit driving errors. Let's get rid of them.

Fixing the Problem

• The university administration needs to rethink its approach to traffic. Admit that, under the present circumstances, we must be driver-friendly rather than driver-hostile. A team with a mandate to do "zero-based" design of a traffic plan must be put in place, with the power to change everything within the law if it makes sense to do so.

• More particularly, let us as a first step think about how to get rid of as many stop-signs as we can on campus. The choice at each intersection should be either a 2-way stop sign, favoring the more heavily trafficked street, or a traffic light. There may be some errors initially, but they can be fixed. I would be especially concerned about what happens in the morning as bikes try to cross Campus Drive at Escondido and other points. Will there be enough gaps in traffic to let that happen? If not, we need a light.

• You might think that we need lights in many places, such as all along Campus Drive under this scheme, and lights are almost as bad as 4-way stop signs (you have a 50% chance of having to stop, and when you do, you stop for a longer time). However, if so, there is a right way and a wrong way to design traffic-light systems. The wrong way, used almost universally in the Stanford area, is to have bumpers to sense stopped cars and flip the light in their favor. The right way is to have staggered lights along the main roads: Campus and Palm Drives in Stanford's case. By having lights flip in blocks, you can have waves of cars going in both directions along Campus Drive, never having to stop. You can similarly time lights along Palm Drive to agree with the light at the Campus/Palm intersection, so once you get on either Campus or Palm you can proceed without stopping. As a bonus, this scheme causes cars to travel in waves, so it becomes easier to cross the main roads on bike or foot.