Casual carpooling reduces transit patronage,
increases pollution

Email From: Miriam Hawley
Date: Mon, 8 Feb 1999 07:43:49 -0800

The Bay Area RIDES report on its casual carpool survey included some crucial information.

[This report is at and continues by clicking "next" or click "index."]

-- 74% of casual carpool passengers and 33% of the drivers used public transit before they began casual carpooling. 87% of the passengers and 54% of the drivers said they would use public transit if they couldn't use a casual carpool for their trip. While only 15% of the drivers of casual carpools said they participate in casual carpooling to save money, a majority of the passengers in these carpools reported that they use casual carpools to save money

-- The net effect of casual carpooling has been to add about 645 cars to the HOV lanes on I-80.

-- 59% of casual carpool passengers get to their pickup spot in a car -- 41% drive alone, 15% are dropped off, and 3% carpool.

My comments:

The cold starts of autos traveling to carpool pickup locations obviate any benefits to air quality from the practice of casual carpooling. (It is interesting to contrast the modes of travel of casual carpoolers to their pickup locations with the ways transbay bus patrons get to their bus stops: almost 80% of people taking a transbay bus walk to the bus stop, and only 6% use an automobile.)

The overall findings of the report demonstrate that casual carpooling does not reduce, but actually increases the number of cars on the road, especially during morning commute periods, with corresponding additions to congestion and air pollution.

Casual carpooling would be difficult to discourage, as the RIDES report concludes. But this report provides no justification for its promotion or for public actions in support of casual carpooling.

Miriam Hawley [ but first delete the X, an anti-spam technique]

Casual carpooling increases traffic congestion

Ron Kilcoyne (written about 1990)

Casual carpooling is a phenomenon in the East Bay: drivers stop at A.C. Transit bus stops to pick up transit passengers enroute to San Francisco over the Bay Bridge. A survey recently conducted by 'RIDES for Bay Area Commuters' showed that casual carpooling is increasing traffic on the Bridge. With 3 people in the car, a driver saves 10 to 20 minutes (at the toll plaza) and 75 cents by using the HOV lanes. In the evening, the driver returns (non-toll direction) without riders.

Proponents of casual carpooling claim that it increases auto occupancy even if only in one direction. Opponents point out that it does nothing to reduce congestion. It merely diverts people from high occupancy transit to lower occupancy autos. The RIDES survey showed 87% of the riders and 37% of the drivers were previously transit users. This translates into 360 more autos that congest the Bay Bridge and San Francisco. In addition, 525 cars switched to the HOV lane, slightly decreasing congestion for the solo driver. A.C. Transit and BART lose about $1 million per year because of casual carpooling. Also lost are toll bridge revenues, part of which go toward transit.

The effects of casual carpooling are the opposite of the purpose of RIDES: to facilitate the reduction of vehicles.

One solution would be to prohibit carpools from using the HOV lanes, and reserve them for buses and vanpools. Carpools can still get a free ride.

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