NewUrbanStreets

Note – This is a followup article to Trees in the Parking Lane on Dallas St and Leaves Stamped in Concrete.

There is another thing we tried in the Dallas St. project to give it a special urban identity. The traffic engineers–correctly applying the requirements of the traffic control manual–said there had to be a continuous white line between the parking lane (with the trees) and the lane of moving traffic. We have enough of the unappealing look of chipped, ragged thermoplastic stripping and the fading painted stripes. Besides, that is so typical and this street needed to have its own character–like many others in downtown Houston–but with a limited budget.

In addition, it would be great if there could be something very distinctive so when a pedestrians visiting downtown walks to stores and restaurants and later returns to the street they know they are back to the street they were on when they went inside. All that is my simple understanding of one of the values of place-making.

To achieve both ends we came up with a stripe made of dots that the traffic engineers accepted. The dots (soon renamed  “buttons”) are 8″ diameter, 2″ tall, domed, precast white-stained concrete cylinders. The short domed cylinders are then mounted in core-drilled holes. The asphalt was chipped out of the core-drilled area and the bottom cleaned to be relatively flat. The precast white concrete was pushed down into an adhesive epoxy material with the epoxy filling the gaps around the sides to secure it in place. See the details from the plans at the bottom of this article.

In the first image on this page you see the area at the tree wells where the precast “button”–as we call it–was epoxied to the surface of the concrete tree skirt so it projects above the pavement. The intent is to indicate to drivers an area that is not to be crossed. In the areas between the trees the button is at the same level as the pavement so cars can pull in to park.

At most of the intersections we have concrete unit-paver crosswalks and the buttons had to cross those pavers to direct the drivers to not start down the lane now filled with trees. Therefore, the white buttons had to be inlaid with the pavers sitting on the sand bed. How well we could insert the precast into the pavers was the “great unknown”, in my view, of all the atypical things included in the Dallas Street project. The pavers are tighthly “locked” into place with the sand in the joints but the grinding action of the diamond-tipped core drill could have loosened them. But that did not happen. The core drill took out a smooth circle; the sand was dipped out; the hole lined with epoxy; and the button dropped in. They are very secure as the epoxy locks the pavers together with the button.  I have seen no failures in this second year.

BTW – We could not find anyone that made precast circles. Anticipating the contractor would find someone to make them or do it themselves we spec’ed them. The low bidder set up forms in their yard and precast them by hand. None of the bidders complained that we had required an item that was not readily available.