American Express Mass Transit Model {#um-models-flows-amex-payg-intro}
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The American Express mass transit model is American Express Pay As You Go (PAYG). It is a delayed authorization model that uses the Expresspay transit policy workflow.

American Express Pay As You Go Model Capabilities and Features {#um-models-flows-amex-payg-function-feature}
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This section describes the capabilities and features of the American Express PAYG model.  
The table lists the mandatory (M) and optional (O) capabilities of this mass transit model.

|                      Capability                       | Requirement |
|-------------------------------------------------------|-------------|
| Dedicated transit merchant category code (MCC) values | M           |
| Population of transit access terminal indicator       | M           |
| Decline expired cards                                 | M           |
| Deny list capability                                  | M           |
| Transaction aggregation                               | O           |
| Account status check                                  | M           |
| Enhanced risk mitigation                              | O           |
| Application transaction counter (ATC) synchronization | O           |
| PAN translation                                       | O           |
[Capabilities of the American Express PAYG Model]

These are the key features of the American Express PAYG model:

* Journeys are multimodal.
* Fares are based on distance.
* Points of entry are contactless.
* Accounts are verified with an authorization for a nominal amount or the maximum fare amount.
* The deny list is checked so that cardholders with previously declined transactions can be blocked.
* Data can be authenticated offline to confirm that the card is valid.
* Multiple card taps and fares can be aggregated into a single payment.
* The deny list is automatically updated every 20 minutes.
* The back office records all trips and fares in order to reconstruct journeys and calculate the final fare.
* When the nominal amount authorization is declined, debt recovery can be performed.
* Standard follow-on payment services can be used to capture, reverse, or void transactions.
  {#um-models-flows-amex-payg-function-feature_ul_isp_3pg_lzb}

American Express Pay As You Go Workflow {#um-models-flows-amex-payg-flow}
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American Express PAYG is a delayed authorization model that uses the Expresspay transit policy workflow. It begins when the rider taps a payment card at the fare collection terminal.

#### Figure: {#um-models-flows-amex-payg-flow_fig_fqh_y5d_j3c}

Pay As You Go Delayed Authorization Model  
![Workflow diagram showing the American Express Pay As You Go Aggregated
transaction model.](/content/dam/documentation/cybs/en-us/topics/payments-processing/card-processing/mass-transit/images/transit-amex-flow-800x600.svg/jcr:content/renditions/original)

1. The cardholder taps the card to enter the transit system.
2. The gate validates the card using offline data authentication (ODA), the card expiration date, and the deny list.
3. When the card is valid, the gate allows the passenger to enter the transit system.
4. When the ODA fails, the card is added to the deny list, and the debt recovery process begins. See [Debt Recovery Workflows](/docs/cybs/en-us/urban-mobility/developer/ctv/rest/mass-transit/um-transit-models-flows-intro/um-models-flows-common-intro/um-models-flows-common-debt-recovery.md "").
5. You send an authorization request for a nominal amount. For authorization and capture options, see [American Express Authorization and Capture Options](/docs/cybs/en-us/urban-mobility/developer/ctv/rest/mass-transit/um-transit-models-flows-intro/um-models-flows-amex-payg-intro/um-models-flows-amex-payg-auth-capture.md ""). Also see [American Express Delayed Online Authorization with EMV Data](/docs/cybs/en-us/urban-mobility/developer/ctv/rest/mass-transit/um-processing-emv-vpc/um-processing-amex-auth-intro.md "").
6. When the authorization is successful, you calculate the fare for the travel period.
7. At the last tap of the day, submit a follow-on capture request for the day's aggregated fare amount.

American Express Authorization and Capture Options {#um-models-flows-amex-payg-auth-capture}
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There are two options for handling American Express PAYG authorizations and captures. Implement the option that suits your business model.

> IMPORTANT  
> American Express requires your payment technology partner (PTP) to support nominal and full value authorizations during the Level 3 certification.

1. Send an authorization request for a nominal amount.
2. During the travel period, collect the rider's tap data to calculate the aggregated fare.
3. Choose the request to send:
   * **Option 1:** When the floor limit is reached, send a capture request to collect the accumulated amount.
   * **Option 2:** When the number of trips exceeds the floor limit, send a delayed online authorization request.
4. After receiving a successful response, return to step 1 to handle subsequent trips and journeys.