This handbook is intended to assist practitioners in assessing indirect effects and cumulative impacts in the evaluation of transportation projects under the National Environmental Policy Act (NEPA). Issues covered in this handbook include: Understanding the definitions of direct effects, indirect effects, and cumulative impacts; gathering the information needed for the analysis; deciding the appropriate scope and level of detail; carrying out the analysis; identifying mitigation opportunities; documenting the analysis; and using the transportation planning process to support NEPA-level studies of indirect effects and cumulative impacts.