JSFiddle - React, Tailwind, and code Playground

HTML

<form>
<table id="vehicle" class="display" cellspacing="0" width="100%" style="text-align: center;">
    <thead>
        <tr>
            <th>Reg No</th>
            <th>Make</th>
            <th>Colour</th>
            <th>Chasis No</th>
            <th>Mileage</th>
            <th>Quantity</th>
            <th>Unit Price</th>
            <th>Actions</th>
        </tr>
    </thead>  
    <tbody>
        <?php
            $vquery = "SELECT * FROM vehicle ORDER BY arrival_date ASC"; // query the person
            $data = perform_query($db, $vquery);
            foreach ($data as $d) {
                $vid = $d['vid'];
                $regNumber = strtoupper($d['reg_no']);
                $model = ucfirst($d['make']);
                $unit_price = $d['purchase_price'];
                $colour = ucfirst($d['colour']);
                $vin_no = strtoupper($d['chasis_no']); ?>
                <tr>
                    <td><?php echo $regNumber; ?>BY658DN</td>
                    <td><?php echo $model; ?>Toyota</td>
                    <td><?php echo $colour; ?>White</td>
                    <td><?php echo $vin_no; ?>JNSAMPLESAMPLE</td>
                    <td><input type="text" name="quantity" style="width: 100%;"></td>
                    <td>
                        <select name="">
                            <option selected>1</option>
                            <option>2</option>
                            <option>3</option>
                            <option>4</option>
                            <option>5</option>
                            <option>6</option>
                        </select>
                    </td>
                    <td>
                        <input type="text" id="unit_price" name="unit_price" value='<?php echo "£" . $unit_price; ?>' style="width: 100%;">
                    </td>
                    <td><input type="radio" name="selectedVehicle"/></td>
                </tr>
            <?php 
            }
        ?>
   ...

JavaScript

rdoBoxes = document.getElementsByName("selectedVehicle"); 

       for (var i = 0; i < rdoBoxes.length; i++) {
           var rdoBox = rdoBoxes[i];
           rdoBox.onclick = function() {
               var currentRow = this.parentNode.parentNode;
               var secondColumn = currentRow.getElementsByTagName("td")[0];

               alert("You have selected Vehicle Reg No: " + secondColumn.textContent );
           };
       }