Image rudely snatched from Andrew Young

I came across an article describing Lego’s intent to open an attraction at the Milpitas Great Mall. I think it’s a wonderful idea, and will bring a lot of economic activity to the area (where I own a home). It will also increase traffic.

But there is are BART and VTA stations opening there soon, which got me to thinking: how can we encourage shoppers to use transit instead of driving? How about by offering them a discount when shopping if they use transit? What if by taking transit to the mall, you could get 5% off your purchases?

There are two main issues: how do you persuade merchants to offer this discount, and how do you determine if a shopper has used transit? Let’s look at one possible solution to the second issue first.

Discount Qualification Criteria

How does a shopper qualify for the discount? The exact rules are less important, but it could be enough to say, "Has the shopper ridden public transit in the region in the last two hours?" The time window and extent of the region can be adjusted.1

Shoppers can show their transit ticket stubs to the merchant, and if it shows use in the last couple of hours, grant the discount. But most transit doesn’t offer stubs, and all agencies encourage use of transit cards, like the Clipper Card.

Instead, merchants can be given a special contactless terminal that shoppers can tag with their transit cards. The terminal is pre-configured to check if a rider has met the discount criteria, without revealing any private info about the shopper, other than the fact that they meet the criteria at this moment.

The terminal would send the shopper’s transit card ID to the card’s servers, and the server would reply with a go/no-go response based on the merchant and transit agency’s agreement.

Incentivizing Merchants

This one’s simple: pay them. Pay them for the discount. Give them rider discount perks for their employees. Give them the terminals at no charge. Create a marketing campaign with materials that allow the merchant to advertise their participation in the green economy.

It’s okay to limit the total amount of the discount. I wouldn’t expect the agencies to pay 5% of the cost of a new car. The discount can apply to the first $100 dollars purchased during the discount window.2


This sort of program should be funded via budgets set aside to encourage ridership, and perhaps via additional fees on car registration or road tolls.

The idea is to keep pushing the levers to gently encourage adoption of mass transit, and to discourage individual driving.

  1. It’s hard to decide what qualifies as “riding transit to go shopping.” The systems often only note the time and location a rider boarded, not when or where they got off. They may have boarded outside the region around the merchant, but disembarked across the street. Using solely a time window of a couple hours is probably a good proxy for the shopper’s transit-riding intent, and it gives them time to actually shop. It’s probably not unreasonable to make the window four hours or even eight hours. 

  2. There are some privacy concerns. It’s easy enough to keep a shopper’s riding data private from the merchant, but to enforce discount limits, the merchant will have to send sales totals to the server, giving the transit agency the ability to collect substantial information about the shopping habits of its riders. There’s no easy way around this, except to put in place a firewall between the agency and the terminal.

    It will probably be necessary for a third party to handle the terminal and servers, providing the service to both merchants and transit agencies (otherwise, each transit agency will have to implement support separately). This third party can be regulated to discard shopping history data beyond the discount window.