Driveways: They’re Not as Simple as You Think!

Posted by on Sep 27, 2016 in Road Safety | No Comments

People are often surprised to find out that they need to obtain a permit before adding a driveway that accesses their property from the highway.  The addition of a driveway could have an adverse impact on the safety and operation of the highway, so a permit must be acquired to ensure that a balance is maintained between the needs of the property owner and the primary purpose of the highway which is to provide a safe and effective flow of traffic.

driveways-1A licensed engineer will prepare the permit which will need to be approved by the highway agency before construction can begin.  It will include a site plan of existing and proposed conditions and statements verifying that all applicable standards are met.  Criteria typically evaluated include stopping sight distance, intersection sight distance, drainage impacts, utility conflicts, driveway width, driveway spacing, and grade.

Both stopping sight distance and intersection sight distance are critical to traffic safety.  Stopping sight distance is the ability of the driver to see down the road beyond their vehicle.  Sufficient stopping sight distance ensures that oncoming traffic will have time to react to drivers entering or leaving the highway or objects on the highway.  Intersection sight distance is the area that needs to be free of obstructions that could block the driver’s view of approaching traffic.  The size of the cleared area depends upon factors such as highway speed, type of traffic control at the intersection, type of vehicles that are most likely to access the property, and the grade of the driveway.  An intersection with a high volume of semi-trailer traffic would require more intersection sight distance than an intersection that would mainly handle passenger cars.  The image below on the left is an example of stopping sight distance; the required distance for the truck driver to see the car in front of him and react to a change in behavior such as braking or stopping must be free of obstructions, such as the crest of the curve.  The image below on the right is an example of intersection sight distance.   The triangular areas shown must be free of obstructions for a determined distance for the driver to observe oncoming traffic before turning onto or crossing the highway.


Property owners will most likely desire to obtain a permit within a certain length of time, but that time period depends on accomplishing several tasks.  Obtaining the permit will depend on how long it takes the engineer to develop a site plan and evaluate the items mentioned above. An application must then be submitted to the governing highway agency for review and processing.  An experienced consulting engineer can help walk a property owner through the permitting steps to increase efficiency.

Once the driveway is in place there should be no need to renew the permit since it has been found to meet all applicable standards.  They may seem like a nuisance, but driveway permits are necessary to maintain a proper balance between the needs of property owners and providing safe and efficient operation of highways.




Leave a Reply