In the fall of 2002, the Planning Office conducted a survey of the MIT community about how people commute to and from campus. We have summarized some of the results here.
The survey included questions about how respondents commuted to and from campus for each day of the week. The data has been divided into four categories according to respondents' affiliation with MIT:
The data for the five days of the week was averaged together, as was the data for the two days of the weekend. Thus values for 'didn't commute' include those who commuted four out of five days (but multiplied by a factor of 1/5) Distance from campus was computed by town, and thus contains some inaccuracies.
Obviously, since most undergraduate students (about 98% of the respondents) live within 5 miles of campus, we can easily imagine that they use human-powered transportation (walking or biking) to get to/from class. The data shows that this assumption is correct.
The assumption about undergraduate students also applies to many graduate students since most graduate students (about 90% of the respondents) live within 5 miles of campus. However, fewer graduate students use human-powered transportation than undergraduates, and furthermore most of the difference is the number of public transportation users. This is presumably because graduate students are much less likely than workers to have a family, and thus be subject to pressures to live in the suburbs and away from easy transit access. On the other hand, the low proportion of driving is probably because most graduate students cannot afford to have their own cars.
When we look at the academic workforce (faculty and research and other academic staff) we see a large change from the tendency of students' selection, presumably because employees live further away than students; about 52% of the respondents live more than 5 miles away from campus while most students live within the area 5 miles away from campus.
The proportions for the non-academic workforce are fairly similar to ones for the academic workforce, except for about 10% moving from human-powered transportation into public transportation. This can probably be explained by the distance between home and MIT; about 60% of the respondents live more than 5 miles away from campus and only about 5% of those who live within one mile of campus, which is about half the proportion of the academic workforce.
Over half of undergraduates go to campus on weekends, and the proportions of their transportation methods are similar to those during the week; most of them use human-powered transportation.
The proportion of grad students that go to campus on weekends is slightly less than half of them, with similar proportions using particular modes except driving; about 17% of weekend commuters drove to campus while about 5% of weekday commuters did so.
Only about 1/4 of the academic workforce commutes to MIT on weekends and almost half of weekend commuters drove to campus.
A very large proportion of non-academic workforce does not commute to MIT on weekends and almost half of commuters drove to campus as well as academic workforce.
Now we look at why people choose the method they choose. First we look at the general breakdown among all modes of travel. Most people care about convenience, and choose the easiest way to commute.
The difference of energy consumption and pollutant emission between transportation modes is shown in the table below (data from Rocky Mountain Institute).
| energy use per passenger (BTU/mile) | CO2 per passenger mile (lb) |
|
|---|---|---|
| transit bus | 4802 | 0.78 |
| carpool (3 passengers plus driver) | 1454 | 0.23 |
| car (driver only) | 5815 | 0.91 |
As we can easily understand, human-powered transportation modes are the most environmentally friendly, followed by public transportation (in this table, bus) and carpool, and driving alone is the least environmentally friendly. Transit data may be skewed by low ridership. Reducing the number of commuters who drive alone is the most effective way to reduce the environmental impacts of the MIT community's commute.
The majority of people that drive alone do not carpool because their schedules prohibit it. It may be possible for MIT community members to use different carpool groups on different days, or only carpool some days. If all single commuters changed to a four person carpool, their annual gasoline consumption and CO2 emission would be reduced by 146,000 gallons and 2,960,000 pounds respectively. However, all single commuters are not interested in carpooling, and if we recalculate the effect brought only by potential carpool users, who currently drive alone but are interested in carpooling or vanpooling, the improvement in gasoline consumption and CO2 emission will decrease to 21,000 gallons and 418,000 pounds respectively. Hence, it is important to better promote carpool and vanpool programs and to help people schedule their work around the carpool or the carpool around their work. As we see below, many people are not aware of programs that are currently offered that make carpooling easier.
The first chart shows why people that use transit use it; the second shows why people that don't use transit don't use it.
Over half of the people that use public transportation use it because of convenience. Similarly, the majority of those that don't use public transportation don't use it because of convenience. This is slightly cynical; perception of public transportation is totally different between users and non-users. Therefore, non-users are unlikely to change their commuting methods into public transportation as long as their current methods are cost-effective.
If all single drivers changed their commutes to public transportation, their annual gasoline consumption and CO2 pollution would be reduced by at least 41,000 gallons and 730,000 pounds respectively, which is less than the reduction brought by carpooling. This is because fuel efficiency of public transportation is less than that of carpooling, at least given the data in the above table. Moreover, not all single commuters are interested in public transportation as well as carpooling. Thus, when we recalculate the effect brought only by potential public transportation users, who currently drive alone but are interested in public transportation, the improvement of gasoline consumption and pollutant emission will decrease to 8,000 gallons and 142,000 pounds respectively.
On the other hand, some of the graduate students who live off campus and use public transportation would live on campus if adequate numbers of dormitories were provided. If half of the off-campus students would do so, their annual energy consumption and pollutant emission would be reduced by 29,000 gallons and 653,000 pounds respectively at best. It is a relatively small improvement in comparison with encouraging carpooling, but it is still significant to try to reduce our commuting impact.
This chart shows the percentage of people that are unaware of various services that MIT provides to make commutes other than single occupancy vehicles easier.
Most students have already chosen environmentally friendly transportation methods. However, some graduate students still have room to reduce their ecological impact of commuting, on weekdays if they are provided an adequate number of dormitories and on weekends if they stop unnecessary driving.
Both academic and non-academic workforces prefer driving alone for their commuting methods far more than students, while a considerable number of them do not know services that MIT provides to make carpooling or transit use easier.
The most effective way to reduce the ecological commuting impact will be to change our commuting modes into public transportation. However, current data shows that public transportation cannot improve more than carpool because it is less energy effective than carpool. We suspect this is because the data includes many empty buses in the average; analyzing full buses and rail cars would probably yield different results. In general, though, we want to encourage people not to drive alone.
NextEnergy use and pollution data from Rocky Mountain Institute